Fitbit heart rate accuracy 2020

Hi there @StephenB427, good to see you around and I'm sorry for the intrusion, hope you dont mind. But I've seen this case with other users. I believe @tractorlegs refers to use the tracker facing inswards. There are a few suggestions to support this way to use the tracker as you can see here: 
Support for wearing fitbit on the inside of your wrist.


Something that works for me when I'm running and I noticed my heart rate is not accurate is to clean any excess of sweat in my wrist and experimenting with how high I place the tracker on my wrist. When you're not exercising, wearing the tracker just above the wrist bone--as you would a watch--typically works fine. However, moving the tracker up a couple inches can be helpful during high-intensity exercises.


I guess with the chest strap, are different technologies that may present variations on the data recorded in comparison to the wristband tracker. Our PurePulse heart rate tracking is the only heart rate technology to offer automatic, continuous wrist based tracking for all-day health insights and workout intensity. PurePulse allows to track workout intensity and calorie burn.


See you around and until the next one.

Which smartwatch has best heart rate accuracy

The last few years have seen numerous announcements of new Smartwatch products featuring a multitude of health tracking features. Tracking heart rate using a fitness tracker on a smartwatch is not new but the mechanisms around photoplethysmography have evolved quite a bit to make these devices more accurate.

Related reading:

In this article, we compare some of the most popular smartwatch brands such as Apple, Fitbit, Garmin, and Xiaomi and provide you with insights from various studies that have focussed on determining the accuracy of heart rate measurement on these fitness trackers.

Since the technology around optical heart sensors evolves at a fast pace, we have chosen to examine the studies that were conducted in the last three years. (2017 – 2020).


Did you know…

Chest straps for monitoring heart rate are often more accurate than wrist-based heart-rate detection.

Polar company founder Seppo Säynäjäkangas invented the wireless personal heart rate monitor in 1977 in Finland.

How does a smartwatch heart rate monitor work?

The optical heart sensor on the backside of your smartwatches works on the principle of photoplethysmography.

Very simply put, blood is red because it reflects red light and absorbs green light. Your smartwatch uses green LED lights to detect the amount of blood flowing through your wrist at any given time.

When your heart beats, the blood flow in your wrist, and hence the green light absorption is greater.

By flashing the LED lights hundreds of times per second, your smartwatch is able to calculate the number of times the heart beats per minute.

The photodiodes next to the LED lights on your watch help with measuring how much of the green light is absorbed.

Optical heart sensors also use infrared light. Apple Watch uses infrared light to measure your heart rate in the background and uses the green LED lights to measure heart rate during workouts and to calculate Heart rate variability.

Fitbit heart rate sensors and VO2 Max

The four important variables that can influence the heart rate measurement are the brightness of the LED light/s, the sampling rate, resting or activity state, and the skin tone.

Selected SmartWatch Heart Rate accuracy studies tell a tale

#1 2017 UT Austin Heart rate study focussed on error rates in heart rate tracking 

This study was conducted by researchers at the University of Austin(1), Texas and the results were published in March 2017. The study examined the accuracy of self-monitoring heart rate devices.

The objective of this study was to examine heart rate (HR) and energy expenditure (EE) validity of 3 popular wrist-worn activity monitors at different exercise intensities.

For this comparative study, the following primary devices were used:

      • Apple Watch
      • Fitbit Charge
      • Garmin Forerunner

The study evaluated the mean absolute percentage error rate of heart rate tracking of these devices. The mean absolute percentage error (MAPE) is a statistical measure of how accurate a forecast system is. It measures this accuracy as a percentage.

Results from the study indicated that the Apple Watch HR had less tracking errors overall when compared with that of Fitbit and Garmin Forerunner.

  • Apple HR MAPE was between 1.14% and 6.70%
  • Fitbit HR MAPE was between 2.38% and 16.99%
  • Garmin Forerunner 225, HR MAPE was between 7.87% and 24.38%.

#2 2017 Cleveland Clinic Study on heart rate accuracy of SmartWatches

Around the same time that the University of Austin was wrapping up its study, Cleveland Clinic working with Yale University(2) published a study examining the variable accuracy of wearable heart rate monitors during aerobic exercise.

For each exercise type, HR was recorded at rest, light, moderate, and vigorous intensity. An agreement between HR measurements was assessed using Lin”s concordance correlation coefficient (rc).

For its study, the researchers used the following fitness trackers:

      • Apple Watch
      • Fitbit Blaze
      • Garmin Forerunner
      • Polar chest strap H7

One of the key findings from this study suggested that heart rate accuracy can vary between devices based on the type of workout/activity that the user is performing.

The study concluded :

  • The best HR readings captured during Biking were from Apple Watch & Garmin
  • The best HR readings captured during Elliptical training were from Apple Watch

Across all exercise conditions, the chest strap monitor (Polar H7) had the best agreement with ECG (rc = 0.996) suggested that Seppo Säynäjäkangas was really ahead of his times when he started Polar.

The overall Rc readings for the other smartwatches were as follows :

  • Apple Watch (Rc = 0.92)
  • Garmin Forerunner (Rc = 0.81)
  • FitBit Blaze = Rc = 0.67

And suggests that the Apple Watch was more accurate than the Garmin or the Fitbit models.

This also shows that your choice of using Garmin to track your heart rate when biking is a pretty solid choice and for serious athletes the polar chest strap is still the wireless gold standard when it comes to monitoring heart rate.Which smartwatch heart rate tracking is most accurate

#3 2020 Duke University Study on the inaccuracy of optical heart sensors

Early this year in February, Duke University(3) published results from their study that examined the inaccuracies of wearable optical heart sensors.

The researchers examined heart rate readings at resting as well as during exercise activities to check if the reading varied between the inactive physical state and the exercise state.

For this study, the researchers used the following devices:

      • Apple Watch 4
      • Xiaomi Mi Band 3
      • Fitbit Charge 2
      • Garmin VivoSmart 3
      • Empatica and Biovotion

Conclusions from the study indicate that different wearables are all reasonably accurate at resting and prolonged elevated heart rate, but that differences exist between devices in responding to changes in activity.

Smartwatch heart tracking accuracy

The study noted that

  • At rest, the Xiaomi Miband 3 had the highest MAE and the Apple Watch 4 had the lowest MAE (10.2 bpm vs. 4.4 bpm, respectively)
  • -During activity, the Xiaomi Miband 3 had the highest MAE and the Apple Watch 4 had the lowest MAE (Mean Absolute error)

This shows us clearly that the efficacy of optical sensors in the cheaper heart rate trackers may not be at par with the best of breed smartwatches.

That being said, if you were using Heart rate tracking as a metric to motivate yourself, then the Miband 3 does its job however if you were looking at the HR metric from a medical perspective, the cheaper option may not fare so well.

This study also confirmed that for a small population of users, skin perfusion and tattoos may not get any HR reading for both Apple watches and other wearables.

For Garmin trackers, Skin tone may affect heart rate accuracy but “Garmin designs our watches to work on all skin tones… the sensor may have to work harder [when more melanin is present in the skin] to find the pulse which can require slightly more battery power.

Also wearing a Garmin watch too tightly or participating in activities that cause flexing of the wrist may lead to more errors in the heart rate readings.

What are the leading Brands doing to improve heart rate detection accuracy?

The leading brands such as Apple, Fitbit and Garmin among others are trying to address the inaccuracies via various initiatives. For one, these companies are signing up for more and more research studies to measure the efficacy of the HR readings. They are also looking at their algorithms and adjusting it for improved accuracy.

A 2018 study had found the Fitbit charge 2.0 consistently underestimated heart rate by 5.9 beats per minute, and the accuracy of Fitbit’s LED heart rate detection is the subject of a class-action lawsuit.

A year later, a 2019 study examined the Fitbit Charge 2.0 and found it pretty accurate when it comes to heart rate tracking during sleep or sedentary periods.

Since then, Fitbit has taken an active role in trying to improve some of the hardware as well as software aspects around its optical heart sensors with the launch of its Pulse Pulse technology 2.0 in its latest Fitbit Sense smartwatch.

Using the all-new multipath sensor, Sense is expected to deliver medical-grade  24/7 continuous heart rate tracking for exercise, sleep tracking, and everything in between.

With Amazon entering the wearables industry with its newly launched Halo band, competition is going to heat up and with that more of these smartwatches are going to become better and accurate as we move forward.


  1. 2017 UT Austin Study on Smartwatch heart rate tracking
  2. 2017/2018 Cleveland Clinic, Yale University study on heart rate measurement
  3. 2020 Duke University Study on Smartwatch heart rate tracking
  4. 2018 study on Fitbit charge 2.0 heart rate monitoring assessment
  5. 2019 study Fitbit Charge 2.0 heart rate assessment during sleep

Niel Smith

I am a technologist with years of experience with Apple and wearOS products and have a Bachelor’s degree in Computer Science. In my day job, I advise fortune 500 companies with their digital transformation strategies and also consult with numerous digital health startups in an advisory capacity. I'm VERY interested in exploring the digital health&fitness-tech evolution and keep a close eye on patents, FDA approvals, strategic partnerships and developments happening in the wearables and digital health sector. When I'm not writing or presenting, I run with my Apple Watch or Fossil Gen 5 LTE and keep a close eye on my HRV and other recovery metrics.

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Best heart rate monitor: chest straps and HR watches compared

Using a heart rate monitor is the best way to get more data from your training sessions, and that's useful whether you're a novice runner, or a serious athlete. Everyone can gain something from monitoring their heart rate.

And heart rate monitors are for more than sport. The latest devices can help monitor your heart rate 24/7, help spot illness, stress, tiredness – and help tell you when to take a break.

We've reviewed and tested pretty much every heart rate monitor on the market – this is our list of picks.

How to buy a heart rate monitor

When people ask us about buying a heart rate monitor we always ask two questions:

What kind of exercise/how important is accuracy?

This is the most important consideration – how do you workout and how much are you relying on the data?

Running and cycling are usually fine for an optical sensor on the wrist, but high intensity workouts and functional fitness (such as CrossFit) is better suited to an EKG chest strap or an optical sensor in a more stable position, such as the upper arm. That's because fast rises and falls in heart rate can be difficult for optical sensors to track, and lots of movement creates signal noise that affects accuracy.

It's also key to be honest with yourself about how you'll use the data. If it's to check how hard you worked out and as a guide to intensity, the slightly less accurate wrist-based sensor can often be good enough for some people.

But if you're using HR to train in real-time, or you need the best quality data possible, only the accuracy and responsiveness of a chest strap will cut it.

What kind of device do you already have?

When it comes to chest straps, most use ANT+, which is only compatible with specialist running watches that use that same connectivity – i.e. Garmin, Polar and Suunto watches.

Those who want to use their phone to work out will need to look for a Bluetooth-enabled strap, which will connect to apps like Strava, Runkeeper and Endomondo. These can be paired directly to a smartphone, and to smartwatches as well.

Which type of heart rate monitor is most accurate?

Chest strap v heart rate monitor watch

Optical sensors explained

The biggest battleground is chest straps versus wrist devices, the latter use an LED array to "see" the blood pulsing through your veins and estimate your heart rate.

Optical sensors are integrated into most wearables from the likes of Garmin, Fitbit, Polar and Apple. They're more comfortable and convenient, and, if you're running steadily, should do the job just fine.

However, when you start ramping up the intensity, doing functional fitness, or HIIT workouts, optical sensors placed on the wrist can't cope with the rapid rises and falls in BPM. They can also be flummoxed by movement of the wrist in exercises, and controversially, dark skin and tattoos, so accuracy can even depend person to person.

Chest straps explained

This is where a chest strap is better - although some find it much less comfy to wear. Chest straps use electrocardiogram (EKG) sensors, which are more accurate and responsive to rises and falls in heart rate, and the relatively steady position on your chest makes the data less noisy. However, you do sometimes have to wet the sensor to get a good signal.

A third way?

However, there is a compromise. There's been a rise of the heart rate arm band, devices that use optical sensors but placed (usually) on the upper arm. This offers a more stable position, which is less likely to suffer signal interference, while still being comfortable.

Best chest strap: Wahoo Tickr X

Price when reviewed: £64.99

Wahoo Tickr X

Wahoo's top-end heart rate monitor has been updated, and it's now smaller, lighter and better for tracking without taking your phone or running watch along.

The new Tickr X weighs just 48g including the strap is one of the lightest you’ll find. It uses ANT+ (used by Garmin devices) and Bluetooth connectivity and can broadcast bpm data to three different devices simultaneously.

But runners will love the extra data the new Tickr X provides.

It can track cadence, vertical oscillation and ground contact time in running activities, and the new Running Smoothness score pulls these metrics together to offer a singular assessment of your running style. It's much the same data as you'll get on Garmins with the Running Dynamics pod, and we love the focus on form and technique.

The TickrX can store 50 hours of workouts on board the sensor itself, so you don’t need to take your phone out with you to get the data – and it will appear in the Wahoo app. And it will track 500 hours before you need to change the battery.

It looks the part, will give you that accurate hit of data and is available at a good price too.

Buy on Amazon

Polar H10

Price when reviewed: £79.50

Polar H10

As we've already mentioned, if you care about accuracy then for us it's still the chest strap and the Polar H10 is the one we've found to be one of the most reliable.

The iOS and Android-friendly strap boasts Bluetooth and ANT+, so you can pair it to a whole host of devices and third party apps, including Garmin sports watches if you like.

It also introduces a modified design, adding silicon friction dots to help keep the strap in place, plus it's a bit more comfortable to wear.

It still uses an ECG-style sensor that detects the electrical activity of the heart to deliver your BPM readings, but a new measuring algorithm and extra interference-preventing electrodes help improve accuracy.

It's waterproof, so you can go swimming with it although it won't track heart rate intervals in the water. There's onboard memory to store a training session, just in case your phone or wearable dies on you.

We've been using it to test against a lot of the new fitness trackers and smartwatches that have landed at Wareable HQ recently, mainly throwing data into Strava and the Polar Beat app, which is built for heart rate-based training. It's still a chest strap we go back to and can comprehensively say it still delivers the goods.

Sample Polar H10 data

Sample Polar H10 data

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Polar H9

Price when reviewed: £52.99

Polar H9

The H9 essentially replaces the older H7, coming in cheaper than the H10 too if you don't want to spend almost £100 for a chest strap.

What's the big difference between the H9 and the H10? There are a few things. It misses out on the new Pro strap, which is designed to offer a more comfortable fit. It sticks with the strap used on the now retired H7. In our time with it, comfort was a major issue. If anything, we preferred the slightly more hugging fit.

It also doesn't offer the ability to store workouts or pair to two Bluetooth connections at the same time. If you can live without those features, you're still getting a heart rate monitor that delivers where it matters.

It's the same ECG-style method of tracking your heart to give you the best accuracy. It has ANT+ and Bluetooth connectivity support and works with a host of third party apps. We've also successfully paired it up with Garmin, Polar and Suunto watches too. You're also getting a 30 metre water resistant rating, making it suitable for tracking heart rate for swimming.

Polar's companion Beat app is great if you're very much focused on heart rate-based training, letting you zone in on the metrics and insights that matter. We've used it for plenty of running (both indoor and outdoor) and like the H10, it's accurate and the most reliable way to get data you can trust.

Sample Polar H9 data

Sample Polar H9 data

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Garmin HRM-Pro

Price when reviewed: £119.99

Best heart rate monitor 2020: watches and chest straps compared

The Garmin HRM-Pro is smarter than your average chest strap that also promises to give you that accurate hit of HR data. So along with measuring your heart rate with an ECG-style sensor, it's also going to serve up a raft of additional metrics to delve into post and during a run.

Those advanced running stats are cadence, vertical oscillation, ground contact time, ground contact time balance, stride length and vertical ratio. If you know what those terms mean (if not, check out our running watch data guide), these can help to identify areas of your technique and running form that could help improve running style and hopefully get you running better and quicker.

Back to heart rate monitoring, and the HRM-Pro connects to devices using ANT+ and has a 5ATM waterproof rating making it safe for the pool and open water swimming. It's powered by the kind of coin cell battery you'll find powering a lot of watches. That should last you up to a year, before you need to pop it out and replace it.

If you participate in team sports, it can also now track additional metrics like steps, intensity minutes and all-day heart rate data.

We've used the HRM-Pro for plenty of testing including putting it to the race test where it was comfortable to wear and crucially delivered the data that mattered. If you've got an ANT+ friendly device and want that extra hit of accurate HR data and advanced running metrics, it's definitely one to check out.

Sample Garmin HRM-Pro data

Best heart rate monitor 2020: watches and chest straps compared

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MyZone MZ-3

Price when reviewed: £79.99

MyZone MZ-3

If you want more from your chest strap, the MyZone MZ-3 goes beyond churning out simple bpm (beats per minute) recordings. You earn points based on your bpm. It's also integrated into a whole host of fitness classes at studios and gyms globally.

Rather than simply scoring highly based on a high reading, the MyZone studies your effort over time and creates a golf-style handicap for your level. Your aim is to better your own performance, and like golf, MyZone adds a gamification element enabling you to compete against others, even at vastly different abilities.

Design-wise, it's your pretty conventional chest strap with a red elasticated strap, which comes in three sizes, along with the module you can clip out. It also has an internal memory - capable of storing 16 hours of data - so you don't always have to exercise while carrying your smartphone, which is useful for gym classes.

It offers a 7-month battery life from a single charge and is waterproof down to 10 metres so you can take it for a swim too.

If you do keep your smartphone nearby, you'll also benefit from the live stats along with the league tables, personal goals and challenges to keep you motivated.

In MyZone-supporting gyms this data often appears on big screen during your classes. The app has improved over the years too, adding new features that puts that heart rate monitor to better use.

Sample MyZone MZ-3 data:

Sample MyZone data

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Garmin HRM-Tri

Price when reviewed: £119.99

Best heart rate monitor 2020: watches and chest straps compared

There are a lot of wrist-based sports watches that claim to offer accurate heart rate monitoring in the water. We are talking about the likes of the Polar Vantage V2 and Garmin's latest Forerunner watches. The Scosche Rhythm24 armband, Polar OH1+ (which can be worn on your goggles) and new Polar Verity Sense promises accuracy on par with a chest strap too. We haven't tested those comprehensively enough to say they do deliver the goods, so for now we are going to stick with a chest strap that does.

The HRM Tri strap from Garmin is a real pro tool for triathletes. It's an ultra-small and light (a mere 49g) heart rate strap that adds considerable bike and running smarts to some of the pool functions of the HRM Swim.

With a built-in accelerometer that'll deliver cadence, vertical oscillation and ground contact time data (like Garmin's HRM Run) while on two legs, plus HR stat storage while actually underwater, this is one of the most rounded tools for the three disciplines out there. Garmin has also ensured there are no exposed seams and all edges are soft and rounded, to prevent rubbing or any wetsuit-doffing difficulties.

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Best HR monitor armband: Polar Verity Sense

Price: £79.99

Heart rate monitors update draft

The Verity Sense sees Polar take the design of its OH1 and OH1+ heart rate monitor armbands and improve to make it a better fit for more workouts.

It uses the same optical sensor technology used in the OH1 devices and offers many of the same features. It now introduces a higher quality strap that can be worn on your upper arm of bicep to deliver heart rate data accuracy comparable with a chest strap monitor.

That strap is machine washable and the cradle that holds it in place solves one issue with the OH1 by preventing it from flipping over. That cradle also doubles as a Bluetooth antenna to increase connectivity range to 150 metres.

There's both Bluetooth and ANT+ connectivity letting you pair it up to a range of apps and other connected equipment, Battery life has been boosted to 20 hours and now has internal memory for 600 hours worth of workouts. Those workouts can now be synced over to Polar Flow, which was previously unsupported.

While the sensor technology remains the same, it's now easier to choose between transmitting data to device, recording a workout on the device or taking it into swim tracking mode. You're also getting a new swim adaptor to make sure it stays securely in place when you're in the water.

Accuracy against a chest strap monitor was very solid in our testing. For runs, indoor rowing sessions and home workouts, it rarely threw out any wild data like many watches have a habit of doing. We'd still opt for a chest strap for supreme accuracy, but the Verity Sense gets very close and should be good enough for most.

It's £10 more expensive than the OH1, which is still available. With bigger battery life, larger internal memory an improved strap design and the same reliable sensor tech, there's some good reasons to make the upgrade and pick it up before other armbands.

Sample Polar Verity Sense data:

Heart rate monitors update draft

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Best of the rest: Heart rate monitor armbands

MyZone MZ-Switch

Price when reviewed: £139.50

MyZone MZ-Switch

MyZone's Switch gives you an armband monitor, wristband monitor and the traditional chest strap kind to offer more versatility in terms of how you get that hit of heart rate data.

It has both ECG and optical heart rate sensor technology onboard with the idea that you use the two different methods on different parts of the bodies for activities where they are best suited to give you the best results. So, for HIIT workouts, stick on the chest strap, for indoor cycling you can wear it on your wrist and use the optical sensor while wearing it on your upper arm will give you good data for runs.

The Switch has both ANT+ and Bluetooth connectivity to connect to a range of devices and apps and does of course work with MyZone's own companion app. There's 36 hours of storage and it's waterproof up to 10 metres, which means you can take it for a swim if you want HR data in the water.

Battery life is anywhere from 3-6 months, with regular use of the optical sensor offering a bigger drain than the ECG sensor. Crucially, if you stick to the recommended wearing positions for different exercises the Switch can give you good data you can rely on. If you like the option of having multiple places to track your heart, this is the one to do it with.

Sample MyZone Switch data:

Best heart rate monitor: chest straps and HR watches compared

Wahoo Tickr Fit

Price when reviewed: £64.99

Wahoo Tickr Fit

Worn on the forearm rather than the chest, many will find the placement of the Tickr Fit more comfortable and favourable than a standard strap just like the Polar Verity Sense.

Unlike the Tickr X, the Fit uses optical heart rate sensors rather than standard electrocardiography. This has been much maligned for accuracy at peak and high intensity, but thanks to the upper arm placement, we found accuracy to be almost indistinguishable from a chest strap.

It'll dish out calorie burn data and is equipped with Bluetooth and ANT+ support so you can pair it with a whole host of fitness apps, smartphones, GPS bike computers and sports watches.

It's a great alternative to a chest strap, has 10 more hours of battery life than Polar's Verity Sense and crucially for an optical sensor, we found it matches up to chest straps in our side-by-side tests. If you hate wearing something on your chest, the Tickr Fit is a great option to consider.

Sample Wahoo Tickr Fit data:

Best heart rate monitor 2020: HR watches and chest straps compared

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Scosche Rhythm24 HR

Price when reviewed: £89.99

Scosche Rhythm24 HR

While the Scosche Rhythm+ 2.0 has recently been unveiled, the Rhythm 24 is the more feature-packed option from the company that first sought to deliver heart rate monitoring from higher up the arm before Polar and Wahoo.

Like its predecessor, the Rhythm24 HR sits on the forearm to track your BPMs. The idea is that there are less motion artefacts that can impact on a reading that can happen further down on the wrist.

It's available in a range of different coloured bands, is waterproof and has the ability to store workouts onto the wearable and then sync it later. The LED lights built-in indicate your current heart rate zone while training and can also indicate when you need to stick it back on the charger.

The Rhythm24 is ANT+ and Bluetooth Smart compatible so you can use it with a whole bunch of third-party fitness apps, sports watches and sports equipment. There's also the Scosche companion app where you'll find dedicated profiles for a range of activities. It's clean, simple and very easy to use keeping you firmly focused on that heart rate data. At 24 hours, it has the longest battery life of the heart rate monitor armbands available now.

We've tried the Rhythm24 HR and the sweat-proof and water resistant wearable passed the high intensity interval test. Plus, it was also very comfortable to wear during our workouts. It's also capable of measuring heart rate in the water as a bonus.

Bottom line, Scosche proves you can comfortably wear a heart rate monitor elsewhere on your body and still get those results you crave.

Check out our Scosche Rhythm24 HR review to find out more about the heart rate monitoring armband.

Sample Scosche data:

Sample Scosche data

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Whoop Strap 3.0

Price when reviewed: £25 a month subscription

Whoop Strap 3.0

The Whoop Strap 3.0 offers something totally different – if you're willing to subscribe to the $25 a month subscription. While it takes the form of a wristband, it delivers better accuracy for exercise when it's placed on the forearm and upper arm to help you get more reliable readings when training.

There's no display, but it will auto-detect exercise, which can be tagged in the app later, so there's no fiddling pre-workout. You will then get full heart rate data from your session, synced into the Whoop app.

But Whoop aims to do more than just track sessions. It also tracks the effect of workouts, using its Strain score. This is done by monitoring heart rate variability after your session - measuring the gaps between heartbeats to see how affected you were. It will try and augment this with activity from the rest of your day, and your sleep, to recommend when you need to rest and when you need to push.

For those whose training is a bit more serious, this is pretty unique data. While Garmin produces comparable information, that is limited to running workouts. So if lifting, CrossFit or other types of sport are your bag and you're willing to invest in the straps to wear it higher up the arm, the Whoop Strap 3.0 is worth taking a look at.

Check out our Whoop Strap 3.0 review

Sample Whoop Strap 3.0 data:

Sample Whoop Strap 3.0 data

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Best sports watch for heart rate: Garmin Forerunner 945

Price when reviewed: £519.99

Garmin Forerunner 945

The Forerunner 945 sits at the top table of Garmin's sport watch line up, and is designed with hardcore triathletes in mind. It makes use of Garmin's latest Elevate optical HR tech - so it's reliable for runs although problematic for HIIT. You can still pair with a chest strap for better data.

You can train in heart rate zones, receive heart rate alerts, and broadcast heart rate data over ANT+ with paired devices. You can go swimming with it of course, but you'll need to pair it with on of Garmin's HRM chest strap monitors to get reliable data in the water.

And it will produce a tonne of useful metrics from you heart rate data. Training Effect, Training Load, recovery and VO2 Max are all gleaned from tracked runs, using Firstbeat's heart rate variability algorithms. It's actionable and interesting data that can help you learn more about your session.

Outside of workouts, you can also perform HRV stress tests to asses how well recovered your body is for taking on your next workout session. Additional heart rate-based metrics including lactate threshold can be unlocked when it's paired with Garmin's Running Dynamics Pod.

In our testing putting it up against Polar's H10 chest strap, it actually fared really well and is definitely an improvement on what we've seen from Garmin's heart rate setup in the past.

Check out our full Garmin Forerunner 945 review.

Sample Garmin Forerunner 945 data:

Sample Forerunner 945 data

HR sample data: Garmin (left) and chest strap (right)

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Best of the rest: Sports watches with heart rate monitors

Garmin Forerunner 45

Price when reviewed: £149.99

Garmin Forerunner 45

Garmin's entry level running watch doesn't scrimp on heart rate smarts – it has a built-in optical heart rate monitor using the company's Elevate technology – the same you'll find on the brand new Garmin Fenix 6.

While it doesn't produce the same amount of analysis from HR data as Garmin's top devices, it will still give you a VO2 Max reading after an outdoor run, and this is tracked in the Garmin Connect app.

It still suffers the same dropouts and inaccuracies as the rest of the Garmin range at high load - so it's best for steady runners. Of course, you can connect Bluetooth and ANT+ friendly chest strap monitors if you need more accurate data.

But at this price, it's a solid performer in the Garmin range.

In-depth: Read our full Garmin Forerunner 45 review

Sample Forerunner 45 heart rate data:

Sample Forerunner 45 heart rate data

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Buy direct from Garmin

Coros Pace 2

Price when reviewed: £179.99

Heart rate monitors update draft

Like the Garmin Forerunner, the Coros Pace 2 from emerging sports watch maker Coros is an affordable option that comes packed with features including a heart rate monitor.

It's optical based setup, with support to pair up external heart rate monitors as well. That onboard sensor delivers all the things you'd expect including continuous monitoring, training in heart rate zones, but also feeds that data into Training Load insights and will serve up VO2 Max scores as well.

Our early experiences with Coros watches and its heart rate monitors weren't great, but things have certainly improved since then. For steady paced runs and workouts, the Pace 2 holds up well for accuracy. Pairing up a chest strap monitor is definitely the way to go if you do a lot of interval and high intensity training, but in general it performed well in our testing.

Coros is always looking at ways to put that heart rate data to better use, so it's one that could evolve to become more useful. If you don't want to spend big on a multisports watch and want a good performing heart rate monitor, this is definitely one to look at.

Sample Coros Pace 2 data

Heart rate monitors update draft

Polar Vantage V2

Price when reviewed: £449.99

Heart rate monitors update draft

The Vantage V2 is the follow-up to Polar's top end multisports watch where it debuted its new heart rate sensor technology to improve accuracy from the wrist.

With the V2, you're still getting its Precision Prime sensor technology, which is LED based using two different color LEDs and a skin contact sensor to make sure it's taking reliable and accurate readings when you get moving.

That sensor fuels a vast array of features outside of the sports watch staples. It powers Polar's rich training and analysis features and also its advanced sleep monitoring, which is up there with Fitbit for accuracy and insights.

Put to the test, the Vantage V2's HR monitor does a solid job overall. It's certainly not free from the odd wild spike or strangely low heart rate and the start of workouts. In general, it does provide reliable data.

You do have that option to pair up an external heart rate monitor, and if you want to make the most of the V2's best features, that's likely the way to go. Though without it, it should serve many just fine as it did in most of our tests.

Sample Polar Vantage V2 data

Heart rate monitors update draft

Best smartwatch for heart rate: Apple Watch Series 6

Price when reviewed: £379

Best heart rate monitor 2020: watches and chest straps compared

We can debate whether you should call the Apple Watch Series 6 a sports watch or a smartwatch, but there's no doubting it's become a solid device for heart rate monitoring – and its latest Watch much like the Series 5 impresses in the heart rate monitoring department. In fact, it might be offer one of the best wrist-based optical sensors we've tried.

From a fitness point of view, we've put it through the same rigorous testing as we do with all of the wearables on this list and it really impresses where a lot of wrist-based monitors falter. We're talking high intensity interval training.

Data is viewable inside of Apple's own Workout app but the benefit of having a strong collection of third party Watch apps means you can also view that data in places like Strava and Runkeeper.

If you don't care about working in heart rate zones though, it's well equipped for taking reliable resting heart rate readings throughout the day and with the addition of an ECG, it's now fit to tap into heart rate readings to detect serious heart issues including atrial fibrillation.

That data can be viewed inside of Apple's own Health app and also be exported to a PDF to be shared with medical professionals.

Along with the improved hardware, Apple has clearly done some software tinkering too to improve the performance of its heart rate monitor in a big way.

While Fitbit and Samsung do offer decent heart rate monitoring solutions on their smartwatches, it's Apple's that we think does the best job of making it all work and it actually does a better job than a lot of sports watches too.

Sample Apple Watch Series 6 data:

Best heart rate monitor 2020: watches and chest straps compared

HR compared: Apple Watch Series 6 (left) and Wahoo Tickr chest strap monitor (right)

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Fitbit Versa 3

Price when reviewed: £199.99

Best heart rate monitor 2020: watches and chest straps compared

With the Fitbit Versa 3 and the design sharing Fitbit Sense, we'd say that its heart rate monitoring is really best suited for all-day monitoring. It can handle steadily paced workouts, but it does falter when you up the intensity. If that's something you're happy with, then it may be worth considering.

Fitbit is using its new PurePulse 2.0 optical sensor technology, where it has grown the surface area that it can capture readings from. That in theory should lead to improved accuracy.

What we found in our testing during running, HIIT sessions and indoor rides and rowing time with it is that is that it can struggle to stay consistent with a heart rate monitor chest strap and can often record higher maximum readings. There were plenty of runs and indoor workouts where it did match up with a chest strap monitor.

If you're interested in having access to medical grade-style heart rate monitoring, the Sense includes an ECG sensor to give you that. It does cost more than the Versa 3 though.

Heart rate on the Versa 3 does fuel other features at your disposal like giving you an insight into your cardio fitness level and letting you know how regular you smash out Active Zone minutes. This is an attempt to shift the emphasis away from nailing step counts to hitting a recommended amount of minutes where you raise that heart rate with exercise.

As we said, it's definitely one better suited to all-day monitoring, but if you train in heart rate zones or take training seriously, it's probably not one for you.

Check out our Fitbit Versa 3 review

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Withings Steel HR Sport

Price when reviewed: £189.95

Withings Steel HR Sport

The Withings Steel HR Sport is a stylish hybrid that will give you a similar performance to what the Nokia Steel HR delivered in terms of heart rate monitor performance and that's a good thing.

If you're thinking, wait, Withings? Yes, the co-founder of Withings bought back the business he sold to Nokia. The Steel HR Sport is the successor to the Steel HR and if you want a reliable heart rate monitor hidden beneath a stylish analogue-style watch, this should be your one.

With the screen baked into the top of the watch face you can now view real-time heart rate data during your workout. Additional heart rate based features include the ability to take VO2 Max measurements to assess your fitness level. Unfortunately you cannot adjust heart rate zones, for anyone planning to rely on it for a HIIT class.

In testing, the experience was very good and it even held up in some interval training where most optical sensors falter badly to keep up with the rapid change in heart rate. Live readouts tended to trail behind the Polar H10 chest strap we tested it against. Once the session was over though, that data seemed to correct itself in the graphs. The final result was exceptionally close; the Steel HR Sport can keep up.

In the companion Health Mate app you'll be able to view your current heart rate data if you're working out with your phone nearby. It keeps things simple when your session is done and you need to pore over the data.

You'll certainly get more advanced heart rate based metrics elsewhere, but in terms of a hybrid that can handle being put to the sweaty test in the gym our out on a run, the Steel HR Sport does a fine job.

You can check out our full verdict on the sleek hybrid in our Withings Steel HR Sport review to find out how its other features fared in our testing.

Sample Withings Steel HR data:

Sample Withings Steel HR data

HR sample data: Withings (left) and Polar chest strap (right)

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Best fitness tracker for heart rate: Fitbit Charge 4

Price when reviewed: £129.99

Fitbit Charge 4

The Fitbit Charge 4 is the latest iteration of the now Google-owned company's flagship tracker and it's packing in the same HR setup as the Charge 3. So expect a similar performance. Like any wrist-based HR monitor, it can struggle at high intensity, but it will still be good enough for workouts in the gym and on the road if you're not too worried about pinpoint accuracy.

It's once again relying on Fibit's own PurePulse technology to deliver features like real-time heart rate bpm readings while working out and the ability to train in heart rate zones. Fitbit has added some useful heart rate-related features like Active Zone Minutes, which now rewards you for hitting certain heart rate zones. You will also get buzzed when you hit a new heart rate zone during exercise.

Much like the Apple Watch, it's not just about using heart rate for exercise here. The Charge 3 also monitors heart rate continuously to assess your current state of fitness through resting heart rate readings.

It also uses that sensor to unlock mindfulness features like stress tracking through guided breathing exercises. The heart rate sensor is also put to use during sleep monitoring to produce additional metrics to help analyse the quality of your time in the land of nod.

In our testing, it's a similar story to what we got with the Charge 3. For some steady runs, it held well against a chest strap but faltered when you throw in high intensity intervals into those runs. Post workout, the Charge 4 was better at analysing data in the app than it was during a workout. When it comes to continuous heart rate monitoring, it's certainly a different story and that real-time data feels a lot more reliable.

If you're put off by the technical graphs of its competitors, Fitbit's app is one of the most accessible ways to track your workouts and HR data too. it's not a perfect tracker by any means, but definitely more reliable than a lot of fitness trackers we've tried. Also, If you're looking for something with a slimmer design that offers heart rate tracking and is cheaper, definitely take a look at the Fitbit Inspire HR and the new Fitbit Inspire 2.

Have a read of our in-depthFitbit Charge 4 review for more insights into Fitbit's flagship fitness tracker.

Fitbit Charge 4 sample data:

Fitbit Charge 4 sample data:

HR sample data: Chest strap (top) and Fitbit (bottom)

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Best of the rest: Fitness trackers with heart rate

Garmin Vivosmart 4

Price when reviewed: £89.99

Garmin Vivosmart 4

The Vivosmart 4 might have been around for a while, but it's still one of the best fitness trackers out there thanks to its slimline design. It's also because it enhances the use of its onboard heart rate monitor to offer more insightful data.

It can of course be used to measure exercise intensity, although you'll be relying on the motion sensors to track that activity as there's no GPS support. There's support to take VO2 Max measurements, so the maximum amount of oxygen your body can utilize during exercise. Just note that you'll need to do a few workouts to get this calibrated.

Like Fitbit's tracker it can also offering continuous heart rate monitoring during the day to deliver those resting heart rate readings that can indicate your current levels of health and fitness.

In addition to that, it'll also take heart rate variability measurements to activate stress tracking and put Garmin's new Body Battery feature to good use. This feature aims to give you a better insight into how well recovered your body is for your next workout session. It does that by taking into account your stress level (measured using heart rate variability), recent physical activity and how much sleep you’ve been getting giving you a score as a percentage.

Performance-wise, the Vivosmart 4 isn't a tracker designed for people with serious athletic ambitions and that's reflected in the performance of the heart rate sensor. It's good for casual users who want to monitor their fitness levels, but it might let you down when things get more intense.

For a surprisingly slender tracker though, the Vivosmart 4 does a whole lot with the heart rate monitor it manages to squeeze in. If you do want something more feature-packed (but minus the Body Battery feature), you can always go for the Vivosport instead.

Check out orour full Garmin Vivosmart 4 review.

Garmin Vivosmart 4 sample data

Garmin Vivosmart 4 sample data

HR sample data: Garmin (left) and Polar chest strap (right)

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Fitness trackersRunningBuying guides

  • We plan to test the new Fitbit Luxe, a “fashion-forward fitness and wellness tracker,” once it’s widely available. The company says preorders will ship in late May 2021.

  • We plan to test the new Fitbit Luxe, a “fashion-forward fitness and wellness tracker,” once it’s widely available. The company says preorders will ship in late May 2021.

    The Luxe has a color display and a jewelry-like look with a stainless steel casing and available bracelet-style accessories, as well as all-day activity tracking, real-time pace and distance, and stress-management scores based on heart-rate data.

    We’re evaluating Garmin’s Venu line of GPS smartwatches built for all-day activity tracking. The recently debuted Venu 2 (45 mm)—as well as the smaller (40 mm) Venu 2S—focuses on new features over the original Venu such as fitness age, sleep score, additional activity profiles (HIIT, indoor climbing, hiking), and a longer battery life (up to 11 days). The more affordable Venu Sq has a rectangular touchscreen. We plan to test both the Venu 2 and the Venu Sq.

    We’re also testing the Apple Watch Series 6, Wirecutter’s upgrade pick among Apple Watches, to evaluate its merits as a fitness tracker.

April 30, 2021

A wearable fitness tracker can help you monitor your steps, strides, sleep, and more. Since 2015, we’ve spent more than two total months running, walking, swimming, cycling, sleeping, and, in short, living with 28 fitness trackers day and night to assess their accuracy, ease of use, and comfort. Although no tracker perfectly recorded every metric it attempted to, we’re confident that the easy-to-use and long-lasting Fitbit Charge 4 is the best option for most people who want to use a fitness tracker to monitor their movements and take steps toward improving their health.

Of all the trackers we’ve tried, the Fitbit Charge 4 is the most intuitive to use, and it’s among the most accurate for measuring steps and heart rate (although accuracy isn’t everything). It reliably detects, nearly always correctly identifies, and automatically begins to record your workouts—running, walking, biking, swimming—after about 10 minutes of activity. The touchscreen display is bright and clear, and clearly labeled icons allow for unfussy menu navigation. The straightforward, concise app lets you parse daily activity data with ease and allows for linking to a robust network of other Fitbit users (which might help keep you motivated). There are more than 20 activity modes, including a new outdoor-workout mode for sports that aren’t step-dependent (like cross-country skiing or kayaking). Within the app, you can also determine which smartphone notifications you’d like to buzz on your wrist. The Charge 4 features an altimeter (which tracks floors climbed) and built-in GPS (which allows for real-time pace and distance data without requiring a phone connection). This model tracks the duration and perceived quality of your nighttime sleep, and it even records naps (not all trackers do). Its battery life stretches for up to seven days.

Battery life: up to seven days (or up to five hours when in continuous GPS mode)
Sleep tracking: yes, including naps over an hour
Water-resistant: yes, 50 meters
Heart-rate monitor: yes
GPS: built in

The Fitbit Inspire 2 has a slimmer, sexier profile than the Fitbit Charge 4. The touchscreen display is bright and vibrant. Like the Charge 4, the Inspire 2 has no mechanical button—squeezing the sides of the screen will wake it up or return it to the home screen. The Inspire 2 does not have built-in GPS (which the Charge 4 does); it measures pace and distance on a walk or a run when connected to your phone’s GPS (meaning you’ll need your phone with you). On a 1.4-mile walk along a measured loop, the Inspire 2 fell behind the Charge 4 on both distance and step-count accuracy, and it was less precise when recording all-day step count. It did perform solidly in our heart-rate tests. Unlike the Charge 4, the Inspire 2 doesn’t have an altimeter, so it can’t track floors climbed. But like the Charge 4, this model offers more than 20 goal-based exercise modes, and it tracks sleep stages (though alarms are programmable only in the app; with the Charge 4, they’re programmable on the device). You can wear the Inspire 2 on your wrist or on your clothes with a clip (sold separately). The tracker boasts a hefty, 10-day battery life—outdoing the battery life of our top pick by three days.

Battery life: up to 10 days
Sleep tracking: yes, not including naps
Water-resistant: yes, 50 meters
Heart-rate monitor: yes
GPS: when connected to a phone

If you’re especially active and you want to keep in-depth records of all your workouts, consider the Garmin Vívoactive 4S. It’s a sporty, advanced fitness tracker with an emphasis on—you guessed it—exercise. The 4S is the smaller of Garmin’s two Series 4 offerings (it has a 40-millimeter screen, versus the Vívoactive 4’s 45-millimeter screen). It’s refined and highly wearable—the 4S is bigger than the two Fitbit models we recommend, but it’s smaller than other watch-like trackers from Garmin and Polar (another brand we tested). Its color touchscreen is clear and responsive (though more muted than those of a few color-screen competitors). And buttons beside the screen make it easier to toggle among workout modes or to start and stop workouts. Overall, the Vívoactive 4S is a step closer to a GPS running watch than the Fitbit trackers we recommend.

Battery life: up to seven days (watch mode), up to five hours (music mode plus GPS)
Sleep tracking: yes, not including naps
Water-resistant: yes, 50 meters
Heart-rate monitor: yes
GPS: yes

Everything we recommend

Why you should trust us

For earlier versions of this guide, we interviewed such industry experts as Jill Duffy of PCMag and Ray Maker of the website DC Rainmaker. Later, we spoke with cardiologist Matthew Martinez, MD, chair of the American College of Cardiology’s Sports and Exercise Council and director of Atlantic Health System Sports Cardiology at Morristown Medical Center, about heart-based biometrics and calorie calculations. We also checked in again with Clinton Brawner, PhD, a clinical exercise physiologist at Henry Ford Medical Center in Detroit, to continue our years-long dialogue about heart-rate monitoring during workouts. We also touched base with Susheel Patil, MD, clinical director of the Johns Hopkins Pulmonary Sleep Medicine Program, to ask some questions regarding sleep tracking.

Amy Roberts is a certified personal trainer, running coach, and regionally competitive runner. She covered activity trackers for Wirecutter for more than three years, watching them evolve since she got her first Fitbit (the One clip-on tracker, now discontinued) in 2013. She also co-wrote our guide to GPS running watches.

Wirecutter senior staff writer Ingrid Skjong is a certified personal trainer and a lifelong runner who has completed five marathons, dozens of half-marathons, numerous shorter races, and a few triathlons. She writes about all things fitness, from Peloton to yoga mats.

Who this is for

Fitness trackers can give you a better idea of how and how much you move your body throughout the day and night. They’re for people who want to set goals to increase daily movement, exercise more often, and improve sleep habits. These trackers (and their apps) are also for people who want a place to log their diets, hydration, and even menstrual cycles—to gain a broader picture of their health. The differences among these trackers are principally in the number of sensors (and therefore features) they offer and (most important) how easy they are to use.

The lines that separate GPS running watches and smartwatches from dedicated fitness trackers are blurrier than ever. GPS watches can now track your activities all day and your sleep at night. Smartwatches can now capture your movement with automatic activity detection and built-in GPS. Some people may still prefer a dedicated fitness tracker for several reasons, though. For starters, fitness trackers are much less bulky to wear than GPS running watches, and they usually cost a lot less. Unlike smartwatches, they can run for up to a week between charges (whereas you generally need to charge a smartwatch daily). And the latest generation of trackers go well beyond just counting steps and recording workouts: They include more smartwatch features than before—from interactive notifications to third-party apps—and additional sensors to provide more-granular detail on movement and sleep.

We want to stress that these trackers are not a replacement for a medical device. If you have concerns about the appropriateness of a new exercise routine or suspect that you may have a sleep condition, see your doctor. And if a high heart rate is a health concern for you, don’t rely on an activity tracker to help manage your condition.

How we picked and tested

Our best fitness tracker picks side by side, including the fitbit charge 4, fitbit inspire 2 and the garmin vívoactive 4S.

Since the first iteration of this guide, in 2013, we’ve put more than 30 trackers through their paces, choosing new candidates for subsequent updates based on new releases, historical testing data, and customer and editorial reviews. Most of the trackers we’ve tested over the years have been wrist wearables, mainly from the biggest players, Fitbit and Garmin (though there are, of course, others in the game). But not everyone wants to wear a bracelet, and the old, clip-style trackers have almost disappeared. So we also tested a few non-wrist options.

Throughout our testing, we aim to answer the following questions:

How easy is it to use and live with? Because these are devices you’re meant to wear all day, every day, we put a lot of emphasis on comfort, wearability, and user-friendliness—of both the device and its companion app. In living with each one, we considered:

  • Is the device comfortable to wear all day and to sleep with all night?
  • Are the device’s menus easy to navigate? Can you decide which workout types (walking, running, cycling, swimming) and data (step count, calories burned, distance traveled) you want to see?
  • Is the app inviting to use?
  • Do smartwatch features work well?
  • Does the battery last as long as promised?
  • Does the device struggle to sync with a phone?
  • Is the tracker waterproof or at least water-resistant, or do you have to take it off before showering or swimming?

How well does it track activities? To gauge how accurately the trackers recorded all-day step count, we wore the devices in pairs, one on each wrist, for two days straight (switching wrists on the second day). And we compared their step-count readings with the results from an Omron pedometer that we knew to be reliable.

We also tested how well the devices recognized activities and how those results appeared in the apps. We took at least one walk and one bike ride of 15 minutes or longer with each tracker, since most devices need 15 minutes or so of activity to trigger a recording. We noted everything we did each day, and we compared the activity the trackers recorded against that written log. We also wore the devices to bed and compared their results against our actual going-to-bed and waking-up times (for sleep duration).

Since most of the devices we tested have built-in heart-rate monitors, we noted the resting heart rates they recorded to see if those figures jibed with what we knew ours to be.

How well does it record workouts? For all of the devices, we tested how well they estimated distance traveled by walking a mile on a treadmill; the devices all use algorithms to estimate stride length, which they multiply by the steps counted. (We also compared their step counts for that mile’s walk against those of our trusty pedometer.) For the devices with built-in GPS—as well as those that can borrow the GPS of a paired smartphone—we walked marked laps in two New York City parks. For our late 2020 and early 2021 round of testing (without access to a treadmill, due to the pandemic), we walked a known loop in Central Park and walked (or ran) a few known distances to see how they compared to the control measure.

For any device that tracks active heart rate during a workout, we performed two separate tests on the treadmill: a five-minute steady-state run at an easy pace, and a six-minute walk-jog-run of two minutes at each pace. We compared heart-rate readings from the device against readings from an older-model Garmin with a chest strap, at 30-second intervals and for two minutes of recovery. For our late 2020 and early 2021 testing, since we didn’t have access to a treadmill, we performed the tests outside, missing the pace specificity that the treadmill provides but approximating the conditions the best we could.

During all of the treadmill and outdoor tests, we noted how easy (or difficult) it was to read the data display mid-workout.

How accurate is your tracker’s step count?

Fitness trackers collect and present all kinds of data, including the number of steps you walk in a day, the kinds of activities you do, the intensity of your workouts, and how well you sleep. But how accurate are they? It depends. Although fitness trackers tend to measure some activities well, they measure others quite poorly—including all-day step count. (On that note, the often-lauded touchstone of 10,000 daily steps seems to be arbitrary at best, though moving more throughout the day is rarely a negative.)

Any device that you wear on your wrist is actually tracking the swinging of your arm, which—when you are walking or running—pretty closely matches what your legs are doing. But humans do a lot more than just walk and run, and these devices can and do perceive any movement your arms make (say, while you’re folding laundry or clapping your hands) as “steps.” In our tests, most of the devices inflated the number of steps we took by 15% to 30%, compared with results we got using our pedometer. Conversely, if your legs are moving but your arms aren’t (for instance, when you’re pushing a grocery cart or a stroller), you might get shortchanged.

You can’t trust “all-day distance covered,” either. We often hear people proclaim, “My [insert wrist-worn device here] says I walked 10 miles today!” But these totals are based on step counts (which we know to be unreliable) multiplied by stride length—another imperfect estimate that the device makes. (You can measure and set your stride length in the device’s app, which will help somewhat.)

These devices can and do perceive any movement your arms make (say, while you’re folding laundry or clapping your hands) as “steps.”

We measured our overall step count with each tracker over the course of two days, wearing the wristband devices on our non-dominant hand to give them the best shot at accuracy. The percentages in the first column of the table below show the daily average of how much each tracker differed from our pedometer’s count. We also wore each tracker for a mile-long walk on a treadmill (again, wearing the wristband devices on the non-dominant hand). The percentages in the second column show how far off each tracker was from our pedometer’s counts on the treadmill. The third column shows how far off each tracker was in measuring the distance (1 mile) that we walked during the treadmill workouts. For our latest round of testing, in late 2020 and early 2021, we didn’t have access to a treadmill, so we walked a 1.4-mile measured loop in New York’s Central Park. Results from this approach are marked with an asterisk in the table below.

How much trackers over- or underestimated step count and distance

Many wrist-worn fitness trackers inflate all-day step counts, in part because they count certain arm movements as “steps.” Asterisks here denote tests done on a 1.4-mile measured loop in New York City’s Central Park.

Despite their accuracy shortcomings, fitness trackers’s measurements do show trends from day to day and week to week, which is useful if you’re trying to be more active. And many devices do automatically recognize and record activities (say, a bike ride or an elliptical session at the gym) reasonably well, if not perfectly. Still, with any tracker, if you want the very best log, use a dedicated workout mode to record your session.

There are also some other measures you should approach with caution. You shouldn’t use the device’s measurements of your active heart rate for training purposes. A tracker’s GPS accuracy (whether the tracker has its own onboard GPS or uses your smartphone’s GPS) is okay but not perfect (GPS rarely is). More-advanced metrics, like breathing rate and blood oxygen saturation, are best viewed as guides and not replacements for medical assessments. Approach calorie counts with similar care, since most of the devices provide a tally of total calories burned that’s based in part on an estimate of your basal metabolic rate. The key word here is estimate.

Our pick: Fitbit Charge 4

A fitbit charge fitness tracker with its screen displaying the time and step count.

The Fitbit Charge 4 (the newest version of our long-running picks from Fitbit’s Charge series) remains our top recommendation for daily activity tracking, thanks to its ease of use, sufficient accuracy, and intuitive app. In our tests, it automatically and accurately detected activities (such as walking versus running). And it bested many of the others when counting steps or measuring distances or heart rates. The touchscreen display, which works along with a haptic “button” on the device’s side, was intuitive to use, allowing us to scroll through menus and make adjustments quickly and easily on the device itself. This model’s app was the easiest to navigate of any we tested, and it was also the most useful. The Charge 4 tracks sleep solidly, too, managing to collect data from naps as well (not all trackers do).

The Charge 4’s activity-tracking features performed well in our tests, quickly and automatically picking up our walks, bike rides, and more after we put in about 10 minutes of movement. (We confirmed with the company that those initial minutes of activity are folded into the final duration.) As with all Fitbit models, with this one you have to check the app to discover what activities your tracker has recorded: The device itself doesn’t list them; they populate the app’s exercise tab. (Your overall daily statistics, like steps, heart rate, and floors climbed, show up on the tracker). As with most trackers, the Charge 4’s daylong step counts ran high in our assessments. (One morning, it showed we had taken 25 steps before we even got out of bed.) On a controlled walk of a measured outdoor loop, however, it undercounted our steps by only one stride. The Charge 4’s heart-rate monitor performed solidly, particularly during interval sets of walking, jogging, and running. (We typically conduct controlled step-count and heart-rate tests on a treadmill, but due to the pandemic, we took them outside.) The Charge 4 records floors climbed with an altimeter, so hills and climbs are recorded.

The Charge 4 has an easy-to-navigate interface. Video: Michael Murtaugh

New to the Charge 4 is a feature called Active Zone Minutes. It is intended to track activity via time spent in three different heart-rate zones (fat burn, cardio, peak), to give you an idea of how hard you’re working. If you don’t reach one of those three, the metric is recorded as “below zones.” The zones are determined by age and resting heart rate. You can enter a custom maximum heart rate in the app using the standard equation (220 beats per minute minus your age), but there are more-accurate ways to calculate that number. You’ll get notifications during exercise as you move in and out of the specific zones. Depending on your workout, this can result in a lot of buzzes; you can turn off the feature within a specific activity mode, such as running, walking, or cycling. Recorded workouts in the app will display the percentages of the workout spent in each zone. Given the margin of error with most wrist-based heart-rate data, it’s best to view the numbers as guides. (It’s advisable to use a chest-strap heart-rate monitor to get the most accurate results.)

The combination of the responsive touchscreen and the side haptic button (that is, not a mechanical button but an inductive sensor that reacts to pressure) makes the device intuitive to navigate. You can set the narrow, grayscale display to any of more than 20 watch faces in the app. The interface is smartly laid out, with simple, scrollable menus that use both labels and icons; some other trackers we tested show only icons, which can be less than clear. To turn on battery-saving “screen wake,” which renders the screen dark until you raise your wrist, press and hold the side button and select the feature. (You can also choose a manual setting, which requires a screen tap each time you want to view. But we found it convenient to have the screen come alive with a lift.)

Fitbit has the best app of any tracker we’ve tested. It’s highly user-friendly, and it connects you to a large and active social network, which may help motivate you to meet your goals.

The Charge 4 has more than 20 exercise modes, including a new outdoor-workout mode, for sports like cross-country skiing and kayaking. These modes include a programmable interval timer (which is useful for interval training) and a swimming function (because of the pandemic, we were unable to access a pool but will test this as soon as possible). For most activities, you can set a goal for time, distance, calories, or heart-rate zone minutes.

The Charge 4 has three GPS options to create maps during outdoor workouts and to provide your real-time pace and distance: built-in (which doesn’t require a phone connection but does reduce battery life), phone (which uses your phone’s GPS capabilities and uses less battery power than than the built-in mode), and dynamic (the tracker chooses the GPS mode based on the location of your phone and whether or not it’s moving with you). The Inspire 2, our runner-up pick, requires a phone for GPS tracking. Like those of other trackers, the Charge 4’s GPS performed unevenly for us. (Read more.)

The Charge 4 offers customizable, encouraging reminders designed to help you hit your daily goals. The basic reminder is based on taking 250 steps per hour, and it will remind you 10 minutes before the hour if you haven’t reached that (you can turn it off in the app). The app goes into further detail, graphing how many hours in the day you met that goal and breaking down stationary versus active time.

Charge 4 fitness tracker's screen displaying the following text message: want to go to laguna today?

Fitbit has the best app of any tracker we’ve tested. It’s highly user-friendly, and it connects you to a large and active social network, which may help motivate you to meet your goals. (We found apps from other companies to be less effective on both counts.) We never felt forced to hunt for details, and we rarely struggled to find a data point. That intuitiveness and clarity can go far if you’re eager to review your data and look for patterns that could help inform lasting, healthy changes. You can use the app to log your food, water, and caffeine intake, and those who menstruate can track their monthly cycles as well. Tips and information on metrics pepper the app. You can also track your mindfulness activities, which include guided breathing drills (accessible on the tracker) and audio meditation sessions (in the app). Health Metrics are new to the app—breathing rate (breaths per minute), heart-rate variability (the variation of time between heart beats), and resting heart rate (all of these are taken during stretches of sleep lasting three hours or longer). In the app, this trio of metrics comes with a “not intended for medical purposes” notice; these types of metrics should be viewed as guides, versus diagnostic tools. An upgrade to Fitbit Premium—which offers additional content like video workouts—promises more in-depth analysis (namely a 30-day view). Fitbit Premium is available for a 90-day free trial, and is $10 per month thereafter.

Three screen captures of the fitness metrics in the fitbit mobile app.

Fitbit’s app was the easiest to use of all those we tested, and it connects you to a bustling social network.

Three screenshots of the fitness metrics on the Garmin app.

Garmin’s app is less intuitive to use; at times we had difficulty finding our information. The social network is also less active than Fitbit’s.

You can choose which app notifications appear on the display, and you can clear the notifications individually or all at once, which is convenient. (Dismissing notification after notification can get very tedious very quickly.) If you use Android, you can reply to text messages with any of five set messages and five emoji (which you can change in the app). If you use iOS, there are no options to respond to texts.

The Charge 4 has robust sleep tracking and seemed accurate when measuring our time asleep, including naps. The Fitbit app offered advice on ways to improve sleep habits, a nice extra. (If you want to focus more thoroughly on sleep, a sleep-tracking app—or even a device dedicated to sleep—may be of interest.) Sleep stages (awake, REM, light, deep) are displayed nightly and are based on heart rate and movement via the accelerometer. They won’t register for shorter naps (the tracker needs at least three hours to pick them up). And they are more of an estimation (versus a medical-grade statistic), using heart rate variability, which shifts as you go from one stage to the next. The app also calculates and logs a nightly sleep score (on a scale from 0 to 100).

Sleep mode—which you can set manually or schedule—turns off “screen wake” for the night and dims the screen. You can also mute notifications and dim the screen during bedtime via the do not disturb mode (though sleep and do not disturb modes can’t be activated at the same time). Alarms are programable on the device and will buzz on your wrist; they can be turned off or snoozed. Thirty minutes before the alarm is set to go off, a “smart wake” alarm finds an optimal time for you to wake up, based on your estimated sleep stage. The alarm vibration is robust even on the “normal” setting; the “strong” setting makes an audible buzzing noise, which could disturb a light sleeper who is in the same bed.

We had no issues syncing the device to our testing phone (an iPhone). The Charge 4 allows for contactless payments (via Fitbit Pay) and control of Spotify from the tracker, though we didn’t try either.

Fitbit says the Charge 4’s battery lasts up to seven days on a charge. After wearing the tracker for two days and two nights, we found that 68% remained—but this was also after using GPS, which does drain the battery. We also like that the battery meter shows as a percentage and as an icon. Icons alone (as on some trackers) can be tricky to decipher.

Flaws but not dealbreakers

The Charge 4 can record more than 20 different types of activity, but you can see no more than six activity modes at once on the device. If your typical routine involves more than that, you’ll find yourself swapping workout types in and out to make sure all is recorded. Though we haven’t tested it in the pool yet, the tracker limits you to setting a time goal for swimming—you can’t set one for distance (our upgrade pick, the Garmin Vívoactive 4S, lets you do this).

Though the Charge 4 often acquired a GPS signal within 30 seconds or less, on several occasions it took more than a minute to connect in dynamic mode (and occasionally did not do so at all). Along a given route, the trace tended to be a little jumpy. The Charge 4 overshot the control distance of one run by 1.25% and fell under by 5.03% on another. It came in 2.14% over the distance on our measured 1.4-mile walk test (a strong showing among its competitors). At least once, the built-in GPS lost connection completely, recording only half a run (though this can be expected with almost any GPS-enabled device). Using built-in GPS does drain the battery; a 2½-mile walk used nearly 20%.

We found the standard plastic band that comes with the Charge 4 to be a bit stiffer than those of some other models we tested (the Inspire 2’s band is softer and slimmer). You can buy additional bands and swap them out quite easily, but they’re not cheap: A more comfortable fabric one runs about $35.

The Charge 4 garners largely positive user reviews. In rare instances, reviewers who gave it only one star have described it as generally “buggy” or suffering from larger problems, like all-out bricking. Fitbit customer service has always been very good about replacing faulty devices under warranty. But once that coverage expires, there’s not much that can be done. This is true of almost all fitness trackers.

Runner-up: Fitbit Inspire 2

A fitbit inspire 2 fitness tracker with its screen displaying the time and steps count.

The Fitbit Inspire 2 is smaller and lighter than our top pick, the Fitbit Charge 4, and it has fewer features (missing additions like an altimeter and contactless payment). But if you want a sleek, simple-to-use tracker, this is a nice, low-profile choice that still delivers plenty. (Fitbit retired its Inspire and Inspire HR, our former runner-up pick, in 2020, replacing them with the Inspire 2.)

Along with its all-day heart-rate monitoring and resting-heart-rate data, the Inspire 2 offers sleep-stage tracking, connected GPS for real-time pace and distance for select workouts (the Charge 4 has built-in GPS capabilities), and more than 20 exercise modes (the same as the Charge 4). That’s in addition to basic all-day activity tracking, automatic activity recognition, and reminders to move. The Inspire 2 lacks the altimeter the Charge 4 has, so it can’t credit you for climbs. By choosing the Inspire 2 instead of the Charge 4, you’re also giving up quick-text replies for Android devices.

Scrolling through the Inspire 2’s menus. Video: Michael Murtaugh

The Inspire 2’s backlit grayscale OLED touchscreen is bright and clear, though we still found it a bit tough to see in especially bright sunlight. (The Charge 4’s visibility was consistently solid.) The included silicone band is a bit softer and more comfortable than that of the Charge 4. Instead of pressing a button to manually wake the screen or return to the home screen, you squeeze the sides of the device and then scroll through the menus. (Unlike the Charge 4, which includes vertical and horizontal swiping to access modes and menus, the Inspire 2 is all vertical.) The Inspire 2 promises a battery life of up to 10 days—three days longer than our top pick. After two days of continuous wear and activity in our tests, the battery dropped to 81%, versus 68% for the Charge 4 in the same timespan (though this was with the use of its built-in GPS, which siphons energy).

A fitbit inspire 2 displaying the following text message: all my people in the crowd, let me see you dance.

Like that of nearly all wrist-worn devices, the Inspire 2’s step count isn’t totally accurate. It performed well in our controlled outdoor walk for step count, coming in just 0.46% under the control (just behind the Charge 4). But its all-day step-count average was about 12% higher compared with the control than the 4’s. As we’ve explained, devices you wear on your wrist track your arm swings, not your actual steps, so they tend to inflate the number of steps you take, sometimes significantly. For instance, the Inspire 2 seemed to rack up lots of “steps” while we folded laundry one day. It registered fast walks with a stroller as bike rides and a workout heavy on kettle-bell swings as a swim. But it automatically acknowledged and accurately recorded other activities—a 30-minute run, a 21-minute walk—with little issue. We weren’t able to swim with the Inspire 2. It has no stroke-detection feature (the Charge 4 doesn’t have that either), but it does allow for setting the pool length for accuracy. It also performed solidly in our heart-rate tests.

As with the Charge 4, the Inspire 2’s sleep tracking reports what it labels as “light,” “deep,” and “REM” sleep; it also reports your time awake and total time asleep, and provides a sleep score. It does not, however, register naps. You need to “sleep” (trackers use your heart-rate and movement patterns to pick up on sleep) for an hour to trigger auto-detection and data. And you need to do so for more than three hours to receive info on sleep stages. If you want to record a shorter snooze, you can add it manually from the sleep screen in the app. Unlike the Charge 4, which allows you to set alarms on the tracker itself, the Inspire 2 requires you to set alarms in the app (though you can turn them off or snooze them from the tracker).

Three white fitbit bands next to the inspire 2.

Few fitness-tracker apps operate as nicely as Fitbit’s app, which you use for all of the company’s wearables, including our picks. Even if you use it only on a more-casual basis, we think the simple app interface makes for a pleasant experience. You can choose from about 20 faces (the same as with the Charge 4) to customize the look of your display.

You can wear the Inspire 2 on your wrist or in a clip (sold separately for $20) on your clothing. In comparison with the Charge 4, the Inspire 2 lacks a few other bells and whistles, such as a weather app, and the ability to use Fitbit’s contactless payment system and control a Spotify account from the tracker.

Upgrade pick: Garmin Vívoactive 4S

Our best fitness tracker for fitness enthusiast, garmin vívoactive 4S, displaying the steps count and date on its screen.

Fitness enthusiasts who are focused on precisely tracking specific workouts in addition to their everyday activities may find the Garmin Vívoactive 4S to be a more practical, streamlined alternative to a GPS running watch. The Vívoactive 4S monitors the basics (steps, heart rate) and the not-so-basics (stress, respiration); it also offers numerous activity modes and a hefty array of exercise instructions, as well as the ability to create customized workouts.

Its color touchscreen is clear and responsive, though it has a slightly muted palette compared with the color touchscreens on other trackers we tested. Two buttons beside the screen allow you to easily toggle among workout modes (top) and general settings (bottom), as well as lap and back functions. Those buttons also add to this tracker’s running-watch-like feel. With inactivity alerts and goal celebrations, though, this Garmin model better fits the fitness tracker mold.

The Vívoactive 4S has a color touchscreen. Video: Michael Murtaugh

The Vivoactive is one of the most accurate trackers we found when it came to steps and distance. And it did well on heart rate, too, performing at the top in our two active treadmill tests—a good sign for on-the-go accuracy. On the workout front, the 4S has more than 20 exercise modes (roughly the same number as the Fitbit Charge 4), including running, biking, yoga, swimming, and climbing; it also syncs to a host of Garmin-generated workouts (Razor Sharp Abs, After-Work Yoga) in the Garmin Connect app. Once you’ve uploaded a workout to the watch, you can play it back, complete with animated demonstrations and a rep counter. We tried a few, and even though nothing beats solid verbal or tactile coaching cues when you’re learning or performing an exercise, the tiny cartoons can be a helpful guide. (You can also create a custom workout in the app and play it back on the watch, but without animation.)

We found the Vívoactive 4S’s activity auto-detection to be a bit uneven. The tracker picked up a 30-minute run just fine but designated a 26-minute, 1.4-mile fast walk as a run. It also recorded two “bike rides,” which were actually walks with a stroller. This isn’t the only tested tracker that mistook our pushing a kid for pedaling a bike. So if you stroller-walk often, know that your step counts will most likely be skewed.

The Vívoactive 4S encourages you to move but also promotes resting in equal(ish) measure. It monitors time asleep (“deep,” “light,” and “REM”), time awake, and respiration; in our tests, its sleep times seemed to line up with what we logged. Like our other picks, it doesn’t automatically register naps. A feature called Body Battery purports to know when you should rest.

If you like controlling a good chunk of your life from your wrist, this may be the device for you. It offers many smartwatch-like features, such as Garmin Pay, the company’s contactless payment system (which we did not try). The Vívoactive 4S also allows you to download playlists or individual songs from the likes of Spotify Premium and Amazon Music and listen through paired headphones. We didn’t have access to either service, but we were able to control podcast playback on our phone from the watch—a handy feature when we were mid-workout. The battery fell to 48% after two days of continuous use; predictably, training, using the music and GPS modes, and, say, putting the screen on the brightest setting will siphon energy.

What about privacy and security?

Health apps and wearables collect a raft of data, which isn’t regulated or legally protected in the same way that other health data (say, from a visit to a doctor) is (by HIPAA). And companies that are negligent with the data they collect don’t seem to incur financial penalties. If you’re intrigued by a device, but privacy questions give you pause, you’re not alone. As part of our research, we reached out to the companies behind our picks and asked them to respond to a series of questions addressing what we think are important privacy and security considerations. “Rule of thumb: lack of response to specific questions about protecting user data is a red flag,” John Scott-Railton, a senior researcher at The Citizen Lab at the University of Toronto, told us in an email. “A company that cares about security should want to reassure users that they are in good hands.” Here’s what the companies told us.

How our picks compare

What is required to sign up?

Fitbit: Name, email address, password, date of birth, gender, height, weight.
Garmin: Name (can be just first name or a nickname), email address, and password is required to generate a new account. When you add a device to your account, the app asks for height, weight, gender, and birthdate.

What user data does the app collect?

Fitbit: Device collects data that helps estimate metrics like steps taken, distance traveled,
and calories burned, as well as heart rate and sleep stages. (When the device syncs with the
app, data from the device transfers to Fitbit servers.) Geolocation information (which can be
denied or turned off in settings). Some Usage information and details on the devices and
applications used to access services.
Garmin: When uploading activities from the device to the app, info collected includes activities and activity data (steps, distance, pace, heart rate, sleep, etc.). If sharing with third-party apps (like My Fitness Pal), info including calories consumed. If location-based services like weather is chosen, the physical location of the device. When syncing, info including IP address, time, date, and geographic location.

What permissions does the app ask for?

Fitbit: Bluetooth access (for phone pairing), contacts (to find friends on Fitbit), location
(mapping workouts and activities), camera (if adding a profile photo). Permissions can be
controlled in the settings of the Fitbit app.
Garmin: Bluetooth access (for phone pairing), location (tracking workouts and activity), camera (if adding a profile photo).

Is data encrypted at rest and in transit?

Fitbit: Yes. Uses technical, physical, and administrative controls. Data is encrypted using at
least AES-128 (advanced encryption standard) and other protocols like TLS (transport
layer security and DTLS (datagram transport layer security).
Garmin: Yes. Uses a variety of industry standard safeguards, personnel, and processes and evaluates its approach to security continuously.

Is data that’s collected by the device or app shared with third parties for marketing purposes?

Fitbit: No. Data sharing does occur in specific situations, including when a user requests it,
to partners or providers that help provide product and services (third-party customer support,
billing), and if required by law.
Garmin: No. Data sharing does occur in specific situations, including when a user asks Garmin to share data with third parties, with third parties that provide services (order fulfillment, etc.), and when required by law in legal contexts.

Is data that’s collected by the device or app used internally for marketing or other purposes? If so, is it de-identified?

Fitbit: No. Users aren’t targeted with third-party ads. Fitbit advertises its own products and
works with advertising partners that might use cookies and other technologies to provide
their services.
Garmin: No.

Can you opt out of data sharing?

Fitbit: Yes. Via account settings and tools, users can manage personal information associated
with their account. (For instance, rescind access of third-party applications that were once
connected to a device or limiting how information is visible to other Fitbit users.)
Garmin: Yes. Users can opt out of receiving notifications from Garmin, unsubscribe to marketing emails, choose what information other Garmin users can see (via account privacy settings), or delete (or not provide) additional details like location, preferred activities, gender, birthdate, height, and weight. Users can manage their data (view, delete, export) on the Garmin website and can access information including account details and permissions consent history.

Does the company participate in third-party security audits and/or bug bounty programs?

Fitbit: Yes. Fitbit utilizes in-house security oversight, third-party assessments, and a public
bug bounty.
Garmin: Customers who believe they’ve identified a security issue can report it via a submission form on the Garmin site or via a public PGP (Pretty Good Privacy) key and a third-party encryption site.

Company privacy policy

Should you get an Apple Watch instead of a fitness tracker?

A person wearing an apple watch that is displaying fitness metrics on its screen.

The Apple Watch has evolved into a one-stop shop, of sorts, for health and activity tracking. But, along with its higher price, the Apple Watch’s battery life gives us pause. The projected 18 hours on the new Apple Watch Series 6 falls far below that of most designated fitness trackers, which often stretch for days (our top pick can go for up to five days without a charge). With the Apple Watch, a daily charge is required. The Series 6 unveiled a handful of new health-related features, including a blood-oxygen sensor (which is not FDA-approved and is meant only for general, non-diagnostic use). An ECG option (which we tried on the Series 5) checks for irregularities in heart rhythm and is FDA-approved. The Health app aggregates all health and fitness data from the watch. You can share workouts with friends and set up competitions. The watch syncs seamlessly to connected fitness equipment like the Peloton Bike+ and the Mirror.

Apple debuted the Apple Watch Series 6 and the Apple Watch SE in September 2020. (Wirecutter’s resident Apple expert, senior staff writer Nick Guy, reviewed them both here; we will test them in a fitness context soon.) We conducted our latest tests on the now-discontinued Series 5 with watchOS 7 (we used the same assessments as we had for fitness trackers and GPS running watches), as well as on the still-available Series 3 and discontinued Series 4. If you already have an Apple Watch, it will work well as a fitness tracker. If you want only a fitness tracker, you can get a very good one—the Fitbit Charge 4—for a lot less money than an Apple Watch.

The Series 5 debuted an always-on display—a feature that serves workouts well. (No more tapping the screen to view heart-rate, distance, and other on-the-move data.) It also adapts to outdoor light, brightening automatically. We were pleased to see that some of the quibbles we had with the Series 3 and Series 4 had been rectified on the Series 5; for example, previously the Apple Watch occasionally detected specific workouts incorrectly and showed erroneous spikes in heart rate.

If you already have an Apple Watch, it will work well as a fitness tracker.

The Apple Watch measures activity differently than other trackers, encouraging you to close a trio of rings each day—a visually engaging way to keep tabs on things. Instead of focusing on step counts, it sets minimum exercise goals (30 active minutes) and aims to get you on your feet at least once an hour for 12 hours of your day. It also allows you to set a goal of “active calories,” which is how it keeps track of your total daily movement. (To arrive at this figure, it estimates your basal metabolic rate and mixes in the movement it detects and your heart rate.) These goals are customizable. If you dig into the interface, though, you can find your step counts. For us, those numbers tended to be on the high side (on three occasions, the counts were 5% to 23% over). In a 1.4-mile measured walk, it registered 1.3% under the control step count and 3.6% above the distance.

The watch triggers a timed workout mode for certain activities—walking, running, swimming, rowing, using the elliptical machine—whenever it detects anywhere from three to 10 minutes’ worth of that activity. This feature worked well for us. On a few occasions, the Series 3 and Series 4 models determined that we were on an elliptical machine when we were really walking carrying an umbrella or a water bottle. We did several walks holding a water bottle with the Series 5, and we found that the glitch seems to have been patched: It registered our movement as an outdoor walk. (It also auto-detected an actual elliptical session just fine.)

Launching a workout mode (you have about 20 to choose from) gives you more accurate data. We tested the Series 5 indoors, for walking and running; it consistently came in ahead of the distance, measuring our 1-mile treadmill walk as 1.07 miles. (Both of our Fitbit picks also overestimated our indoor walking and running distances in our testing.) To record outdoor runs, an Apple Watch uses either its onboard GPS or the GPS from your phone, the latter of which saves battery life. (The Apple Watch ideally secures a GPS signal when you launch the Workout app; it doesn’t give a confirmation when it locks on a signal.) Our results were within the margin of error expected with GPS tracking (our 1.4-mile GPS walk came in at 3.6% above the distance). In the pool, the Series 5 watch nailed our total distance and detected stroke types perfectly, producing some of the most seamless swim tracking we experienced.

The active-heart-rate monitoring is where we saw a marked improvement in the Series 5 over the Series 3 and 4 Apple Watches. On both our treadmill heart-rate tests, as well as on outdoor runs, the Series 5 readings were consistent and fairly accurate in comparison with those on our older-model Garmin chest strap. (The watch performed near the top of both of our active-heart-rate tests.) Unlike with the Series 3 and Series 4 watches, we didn’t experience any odd spikes. It struggled a few times to detect our heart rate, both in workout mode (outside and inside) and via the general heart-rate screen, but cinching the watch tighter helped.

Apple’s privacy policy is straightforward, and its security standards are on a par with Fitbit’s. And Apple is clear about the permissions you grant and the data you share.

The Apple Workout app facilitates workouts on the watch, and the Fitness app allows you to parse workout and activity data on your phone. Apple launched Fitness+, its subscription-based workout-streaming service, in fall 2020; we will test it soon. It features a variety of workouts by a variety of trainers, as well as guided audio walks, for $10 per month. Apple Watch also introduced a built-in sleep app in fall 2020; it is simple to set up and emphasizes adhering to a sleep schedule. But it reports relatively pared-down sleep metrics (time asleep, average time asleep, and average time in bed, with no sleep stages). See Wirecutter’s review of this and other sleep-tracking apps.

What to look forward to

We plan to test the new Fitbit Luxe—a “fashion-forward fitness and wellness tracker”—once it’s widely available. (The company says preorders will ship in late May 2021.) In addition to all-day activity tracking, real-time pace and distance, and a stress-management score based on heart rate, the Luxe has a color display and a jewelry-like look with a stainless steel case and available bracelet-style accessories.

We’re also evaluating Garmin’s Venu line of GPS smartwatches, which are built for all-day activity tracking. The recently debuted Venu 2 (45 mm)—as well as the smaller (40 mm) Venu 2S—focuses on new features over the original Venu such as fitness age, sleep score, additional activity profiles (HIIT, indoor climbing, hiking), and a longer battery life (up to 11 days). The more affordable Venu Sq has a rectangular touchscreen, more than 20 sport modes, and a version that supports onboard music storage. We plan to test both the Venu 2S and the Venu Sq.

We’re also testing the Apple Watch Series 6, Wirecutter’s upgrade pick among Apple Watches, to evaluate its merits as a fitness tracker.

In addition, we plan to test the Fitbit Versa 3 smartwatch, which has an always-on display, built-in GPS, and a promised six-day battery life. Its advanced health-related features include an SpO2 sensor (which monitors blood-oxygen levels) and the ability to measure heart-rate variability (HRV) and skin temperature variations overnight.

We also plan to test Fitness+, Apple’s subscription-based workout-streaming service. We will compare it with Fitbit Premium


2020 rate fitbit heart accuracy

Fitness trackers' heart rate monitoring accurate enough for most, study says

Story highlights

  • A small study finds that some activity tracker heart rate monitors are more accurate at rest
  • The study measured the devices' performance against an ECG
  • Researcher: "We've had so much advance in technology during such a short period"
When tested alongside electrocardiograph (ECG) technology, devices from Fitbit and Mio performed reasonably well at measuring resting and active heart rates, according to a study published Monday in the Annals of Internal Medicine.
"It's very exciting because we've had so much advance in technology during such a short period," lead researcher Lisa Cadmus-Bertram said. "These trackers are such an enormous improvement over what we used to have."
For the small study, Cadmus-Bertram and her team at the University of Wisconsin looked at how the trackers worked for 40 healthy middle-age adults, compared with an ECG and against each other. The participants wore four devices during the test: a Fitbit Surge, a Fitbit Charge, a Mio Fuse and a Basis Peak smartwatch.
Compared with the ECG reading, wearable products varied in their accuracy. The Fitbit Charge performed the best at rest, measuring within 5 beats per minute of the ECG reading 95% of the time. The Basis Peak activity tracker was shown to be within 22.6 bpm of the ECG reading during the 10-minute resting test.
Accuracy lessened in all of the tested devices during increased activity. The monitors were off by a range of 20 to 40 beats per minute compared with ECG measurements. The findings that devices were more accurate during rest are similar to what previous research has found.
Although data were not provided to show readings at each measured time, Cadmus-Bertram suggested that outliers -- numbers well outside normal readings -- may have caused a wider range.

Critics question heart rate monitors

Critics, however, say that the devices are not performing up to their advertised promises and could supply users with dangerously inaccurate information.
Questions about the devices and their accuracy sparked a class-action lawsuit in 2016 over the technology in Fitbit trackers. The lawsuit was filed on behalf of people who bought Fitbits especially to help track their heart rates, whether for health reasons or to make sure they are getting the most out of their workouts. The lawsuit is ongoing.
"However accurate they may be at rest, the Fitbits are wildly inaccurate as heart rate monitors when worn during moderate- and high-intensity exercise, which is precisely the purpose for which Fitbit (in particular) markets them to consumers," said Jonathan Selbin, one of the attorneys who filed the lawsuit.
Physicians and researchers note that the trackers aren't medical devices. Selbin and others point out that Fitbit, in particular, "claims to be a 'Digital Healthcare Company' and is actively trying to get corporations and insurers to make health care decisions based upon data they collect."
Researchers and physicians said the technology has a long way to go. Dr. Nisha Jhalani, a cardiologist at NewYork-Presbyterian/Columbia University Medical Center, who was not involved in the new study, noted that the technology in ECG machines and LED-based activity trackers is entirely different.
"Electrocardiography, or ECG, involves placing electrodes on the skin surface to measure electrical impulses generated by the heart muscle itself. The LED technology used in fitness trackers is an indirect measurement looking at the changes in light reflection through the skin during each heartbeat," she said.
If you've ever worn a wrist heart monitor, you may have noticed a time or two during exercise when your heart rate read inaccurately low for a few ticks before getting it right. These hiccups are one reason, researchers say, why the range of accuracy of these devices is so wide.
"A tracker will give you the occasional crazy reading, but most of the readings will be quite a bit closer than that," Cadmus-Bertram said.
Overall, researchers and experts are encouraged by the improving technology and continue to promote the use of fitness trackers to provide more information about a user's health.
"Fitness trackers are a great way to make people aware of their activity level throughout the day," Jhalani said. "Oftentimes, our perceived activity is much more than actual time spent we spend moving, especially people whose jobs involve sitting at a desk for hours at a time."
Heart rate data, she says, can be an empowering tool that can allow users to be more aware of their heart health and overall fitness.
"It is good for people to see their heart rate, both at rest and with exercise. Low resting heart rates, in the 60 to 70s bpm range, are considered generally healthy. High resting heart rates, especially when close to 100 bpm or higher, can be a sign of high stress levels or other medical conditions," Jhalani said.
"How quickly the heart rate goes back to normal after exercise also holds a lot of information. Quicker indicates better cardiopulmonary fitness level."
The compact, convenient and more stylish design achieved by using LED technology versus ECG comes with a few tradeoffs.
"LED technology can be affected by variables such as how loosely or tightly the tracker is worn, the user's skin tone or any other interference between the sensor and the skin. It can also become inaccurate with motion, which is why it doesn't fare as well as ECG with exercise," Jhalani said.
In response to the new study, Fitbit said in a statement that its trackers "are not intended to be medical devices and, unlike chest straps, wrist-based trackers fit conveniently and comfortably into everyday life, providing continuous heart rate for up to several days without recharging (vs. a couple hours at a time) to give a more informed picture of your overall health."
Representatives from Mio also emphasized that the product is a consumer device. "We need to make understanding heart rate easier for the average consumer," the company said in a statement. "This opportunity defocuses the importance of needing to know the exact heart rate at any one time, and rather put emphasis on understanding what getting your heart rate up does for your health over time."
Representatives from Basis could not be reached; the fitness tracker used in this study was recalled in September. According to the company's website, the recall is "because the watch can overheat, which could result in burns or blisters on the skin surface."
As a commercial product, Jhalani said, the overall impact is a positive one. "I think it keeps people from becoming complacent and empowers them to work towards a healthier lifestyle."
"While you wouldn't want to rely on a commercial tracker if you need absolute precision during exercise," Cadmus-Bertram said, "there's also no reason for the general public not to use it for feedback and motivation."

Wrist-worn activity trackers such as Fitbit don’t reliably assess heart rate, a new study finds.

While the devices may have some legitimate benefits, they shouldn’t be used for medical purposes, researchers suggest.

Evaluating four wearable activity trackers from Fitbit, Basis and Mio, the researchers compared results to those from an electrocardiograph (EKG). They found results varied among the different models and were much less accurate during exercise than at rest.

“These devices are probably good enough to inform consumers of general trends in their heart rate -- high or low -- [but] it’s important to have more accurate information when physicians are relying on this data to make decisions on medications or other tests and treatments,” said Dr. Mitesh Patel.

Patel is an assistant professor of medicine and health care management at the University of Pennsylvania. He wasn’t involved in the study.

However, the study’s lead author cautions against making too much of the discrepancies.

“At any moment, the tracker could be off by a fair bit. But at most moments, it won’t be,” said Lisa Cadmus-Bertram, an assistant professor of kinesiology at the University of Wisconsin at Madison.

“The heart-rate feature performed better at rest,” she said. “They’re not as precise during exercise.”

A 2014 survey by PricewaterhouseCoopers found that 20 percent of American adults owned a wearable activity tracker.

For the new study, 40 healthy adults, aged 30 to 65, were recruited to test the Fitbit Surge, Fitbit Charge, Basis Peak and Mio Fuse.

Generally, when compared with the EKG results, the activity trackers were near the correct mark, Cadmus-Bertram said. But occasionally, their estimates of heart rate could swing too high or too low.

At rest, the Fitbit Surge was most accurate; Basis Peak was least accurate, the study authors said.

During exercise on a treadmill at 65 percent of maximum heart rate -- defined as 220 beats per minute minus age -- accuracy suffered more.

The monitors could overestimate heart rate by as much as 39 beats per minute (Fitbit Surge), or underestimate it by as much as 41 beats per minute (Fitbit Charge), the study found.

The findings support those of a study released last month at the American College of Cardiology annual meeting. Depending on the type of activity, the wrist devices were up to 34 beats per minute off, those researchers found.

Again, the devices were least accurate during exercise.

Some wrist-worn activity trackers use a light-emitting diode, or LED, that measures heart rate by detecting changes in the amount of blood in the skin.

Patel said accuracy may be a problem because the devices move around on the arm, especially during exercise.

Meanwhile, Fitbit’s maker said its fitness trackers aren’t intended to be medical devices. The company issued a statement in response to the new study.

“We conducted extensive internal studies which show that Fitbit’s PurePulse technology performs to industry standard expectations for optical heart rate on the wrist. Fitbit devices were tested against properly calibrated industry standard devices like an EKG chest strap across the most popular activities performed worldwide -- including walking, running, biking, elliptical and more.”

Cadmus-Bertram cautioned that the data for the new study were collected about a year ago.

“Not only have newer models since been released, but the algorithms behind the data are presumably being updated and improved on a regular basis,” she said. “So the results we found might be different if we did the study again now.”

In general, she’s remains a fan.

“On the whole, fitness trackers still provide a tremendous amount of useful information to the average user who just wants some feedback to help them to increase their exercise level,” Cadmus-Bertram said.

The study findings were published online April 11 in the Annals of Internal Medicine.

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The best heart rate monitors and watches (September 2021)

Jimmy Westenberg / Android Authority

Table of contents

Your heart rate is an essential metric for leading a healthy lifestyle and improving your fitness training. Thankfully, tracking your heart rate is pretty easy, as most activity trackers and smartwatches come with a built-in heart rate monitor. This offers a very convenient way to measure your heart rate quickly, though no wrist-worn tracker will ever be perfectly accurate (read this explainer to find out why). Fortunately, there are also dedicated chest straps for heart rate monitoring if you’re looking for something a little more accurate.

But with so many different heart rate sensors on the market, which one should you buy? We’re here to help! We’ve rounded up the best heart rate monitors in products like chest straps, running watches, and fitness trackers.

How to choose the right heart rate monitor for your needs

People need heart rate monitors for different reasons. Some simply need to keep an eye on their resting heart rate throughout the day, others need it for sleep tracking, and some people need the most accurate heart rate data possible. But not all heart rate sensors are created equally, and the model you choose will depend on your specific needs.

If you’re after the most accurate heart rate data during your workouts, you’ll want to buy a heart rate monitor chest strap. Chest straps are more accurate than wrist-worn wearables and are able to more quickly pick up on some of the nuances when you’re working out.

If you’re after all-day heart rate monitoring or would like something to track your data during sleep, you should opt for a wrist-worn fitness tracker or fitness watch. Most modern wearables can track your resting and active heart rate throughout the day. While they might be more convenient than a chest strap, they’re also less accurate. Many factors can sway wearables’ heart rate data, such as skin tone, the amount of hair you have, and how you wear it on your wrist. Not that those factors don’t affect chest straps, but they’re more prevalent on wrist-based heart rate sensors.

The best heart rate monitors and best heart rate monitor watches

  • The Apple Watch Series 6 is the best heart rate monitor watch you can buy. During the testing period, the Apple Watch provided nearly identical results to those of the Wahoo Tickr X chest strap.
  • The Withings ScanWatch is a great heart rate monitor watch to buy for keeping up on your all-day heart health. It can monitor your ECG and blood oxygen levels, too.
  • The Garmin Fenix 6 Pro offers reliable heart rate readings for all-day resting heart rate, active readings during workouts, and at night.
  • The Fitbit Charge 4 is our favorite fitness tracker on the market, and it has a fairly accurate optical heart rate sensor onboard.
  • The Polar H10 is the best heart rate monitor chest strap you can buy. It’s the most accurate one we’ve tested.
  • The Wahoo Tickr X (2020) comes in second place in our list of the best heart rate monitors. The 2020 model is smaller and lighter than the original.
  • The Garmin HRM-Pro is the best heart rate monitor chest strap for those already in the Garmin ecosystem. The HRM-Pro has Bluetooth, advanced Running Dynamics, and storage for offline workouts.
  • The Scosche Rhythm 24 is a few years old, but still a fantastic heart rate sensor armband. The Rhythm 24 specifically offers great battery life and plenty of storage.

Apple Watch Series 6

Jimmy Westenberg / Android Authority

The Apple Watch Series 6 has one of the best wrist-based heart rate sensors we’ve ever used. Seriously.

During our testing, the Apple Watch kept up with our Wahoo Tickr X chest strap quite well, even during interval runs and HIIT workouts. Sure, it tripped up when our heart rate climbed above ~170bpm, but that’s to be expected.

Furthermore, the Apple Watch Series 6 syncs with many other popular fitness apps, so you can continue using Strava, Training Peaks, and other apps if Apple’s Fitness app isn’t your favorite.

Check out our full review to learn more about the Apple Watch Series 6.

Withings ScanWatch

Jimmy Westenberg / Android Authority

If you want a good heart rate monitor watch that is more focused on daily heart health as opposed to workouts, you’ll want to check out the Withings ScanWatch.

The ScanWatch’s heart rate sensor will be fine for most people during workouts, but it really excels in its residual heart-monitoring features. It has a medically certified ECG monitor and SpO2 sensor. Later in the year, it’ll receive certification for sleep apnea detection. In our review, we called it one of the most sensible wearables you can buy. However, due to the medical certification process, it’s only available in select countries, and the US isn’t on the list at this time.

Withings ScanWatch

The new Withings ScanWatch is taking health tracking to the next level. It has built-in ECG and SpO2 sensors to help detect early signs of AFib and sleep apnea. Plus, it acts as a hybrid smartwatch, giving you notifications, HR data, and more on your wrist.

$249.99 at Amazon$249.99 at Withings

Check out our full review to learn more about the Withings ScanWatch.

Garmin Fenix 6 Pro

Jimmy Westenberg / Android Authority

The Garmin Fenix 6 Pro is one of our favorite running watches, and that’s primarily due to its generally accurate and reliable heart rate monitoring.

Garmin’s latest-generation Elevate heart rate sensor provides heart rate data for the company’s scarily accurate Body Battery energy monitoring feature, as well as all-day heart rate, heart rate variability data, and advanced sleep monitoring. We’ve found the Fenix 6 Pro’s heart rate sensor to be in line with other wrist-based heart rate sensors in testing. Unfortunately, the Fenix 6 Pro’s exorbitantly high price tag doesn’t get you the best of the best heart rate sensor out there, but it will be more than good enough for most people.

The Fitbit Charge 4 is the best fitness tracker you can buy, and it has a decent heart rate sensor. During our testing, the Charge 4 was mostly able to keep up with the Garmin Forerunner 245 Music during interval runs but fell behind a bit with quick sprints.

Fitbit threw in some additional heart rate features with this new fitness tracker. First, Active Zone Minutes is Fitbit’s new way of making sure you’re getting enough weekly exercise. The Charge 4 will notify you of the time spent in each heart rate zone after your workout. The goal is to reach the American Heart Association’s recommended 150 minutes of moderate to vigorous activity each week. And after each GPS-enabled workout, you’ll also see a new workout intensity heat map in the Fitbit app that shows your running or biking route as well as which heart rate zones you were in at any given time.

Check out our full review to learn more about the Fitbit Charge 4.

Polar H10

Coming in at just under $90, the best heart rate monitor chest strap you can buy right now is the Polar H10.

Polar has made a name for itself by producing high-quality, accurate heart rate sensors, so it should come as no surprise that the H10 is at the very top of our list. The H10 uses an entirely new algorithm from previous Polar monitors, and the included Polar Pro strap has been updated as well. It includes extra “interference-preventing electrodes” to help make sure heart rate data is accurately captured. It also sports a new buckle mechanism and silicon dots to help keep it in place when you’re working out.

The H10 also offers quite a few new improvements over its predecessor, the H7. The H10 can now receive over-the-air software updates, features enough built-in memory for one training session, and up to 400 hours of battery life.

Polar H10

Packing a long battery life, a more comfortable design, and a new algorithm, the Polar H10 is the best heart rate monitor chest strap you can buy.

$89.99 at Amazon

Jimmy Westenberg / Android Authority

We’ve used the older Wahoo Tickr X chest strap in just about every fitness product review over the last couple of years. The 2020 Tickr X chest strap is even better.

The new model is smaller and lighter than the original and features a more integrated design that should keep the tracker in place while you’re exercising. The indicator lights have also moved to the top of the tracker module.

There are two bigger functional upgrades to the Tickr X (2020). First, it supports multiple simultaneous Bluetooth connections. It can also display in real-time ANT+ running dynamics when paired with a GPS fitness watch.

Wahoo Tickr X

The Wahoo Tickr X ticks all the boxes for those seeking a sleek, chest heart rate monitor with support for multiple apps and devices.

$79.99 at Amazon

Garmin’s HRM-Pro is its best heart rate sensor chest strap yet and is best suited for those already in the Garmin ecosystem. The HRM-Pro is essentially an upgraded version of the HRM-Tri, which previously held this spot on our list. The HRM-Pro is now geared towards more types of athletes, not just triathletes.

This chest strap finally has Bluetooth, as well as advanced Running Dynamics and storage for offline workouts. The latter feature is certainly overdue, but we’re happy users can finally record workouts phone- and watch-free and sync at a later time.

Garmin HRM-Pro

The best Garmin heart rate monitor you can buy comes with Bluetooth, advanced Running Dynamics, and storage for offline workouts.

$129.99 at Amazon

The Scosche Rhythm 24 heart rate monitor armband is a few years old at this point, but it’s still one of the best heart rate monitor armbands you can buy.

It’s not the best-looking armband you can buy, nor is it the smallest, but it comes with some additional features over Scosche’s Rhythm Plus sensor. The Rhythm 24 has NFC for quick-pairing with certain gym equipment, 24 hours of continuous battery life with LED indicators, and onboard memory with up to 13 hours of training stats.

Scosche Rhythm 24

The Scosche Rhythm 24 is an armband packing ANT+ support, NFC for quick pairing with gym equipment, and 24 hours of battery life.

$99.99 at Amazon

Honorable mentions

Those were our top picks for the best heart rate monitor chest straps and heart rate monitor watches. Here are a handful of devices that nearly made our list.

  • Garmin Venu 2: The Garmin Venu 2 is the first wearable with the company’s new fourth-generation Elevate heart rate sensor. While the sensor could use some refining, it’s an overall capable tracker and mostly accurate for high-intensity activities.
  • Fitbit Sense and Versa 3: The Fitbit Sense and Versa 3 feature Fitbit’s new PurePulse 2.0 optical heart rate sensor. The sensor itself is just okay, but you’ll really want to pick up the Sense for its ECG and overnight blood oxygen monitoring.
  • Xiaomi Mi Band 6: The Xiaomi Mi Band 6 actually has a decent heart rate sensor for the price. The Xiaomi Wear app isn’t our favorite, but the device itself is a capable budget fitness tracker.
  • Garmin Forerunner 245 Music: The Forerunner 245 has the same Garmin Elevate optical heart rate sensor as Garmin’s top-tier running watch, the Forerunner 945. In our testing, the 245’s sensor performed noticeably better than Garmin devices that came before it.
  • Garmin Vivosmart 4: We found the Vivosmart 4’s heart rate sensor to be acceptable but not quite on par with Garmin’s newer devices.
  • Whoop Strap 3.0: The Whoop platform provides plenty of interesting data on recovery, strain, and sleep, making for a great training platform. However, the Whoop Strap 3.0 itself provided inaccurate heart rate data during our review.
  • Samsung Galaxy Watch 4: The Samsung Galaxy Watch 4 is a fantastic smartwatch and has a bevy of fitness features. Tts heart rate sensor was more accurate than its predecessor in our testing, but it is let down by some Samsung-specific features.

The BestFitbit, Fitness, fitness trackers, Garmin, Polar, smartwatches, Wearables, Withings


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