Think all heart rate trackers on smartwatches are created equal? Think again. The performance of heart rate trackers differs considerably across manufacturers and there’s three reasons why this can be the case.
The first reason is hardware. All smartwatches use an optical heart rate sensor which detects the blood pulsing through your veins. But different manufacturers use different sensors, and some are better than others.
The second reason is software, because while the sensor itself collects data, it’s the software which number crunches the data into information. Software can give an inaccurate set of results if the algorithm isn’t right.
The third and most common reason is fitment. Because optical heart rate sensors must be located on the back plate of the watch, the watch needs to be fit nice and flat on your wrist and be fitted right. If it’s too tight this can restrict blood flow and give inaccurate results, but if it’s too loose the optical sensor won’t work.
And so, the best smartwatches for heart-rate tracking have a trio of characteristics: an accurate optical heart rate sensor, good software, and good design. Regarding the latter, the device should fit comfortably on your wrist and register heart rate tracking 90% of the time. A 10% window of failure is considered normal.
Which watch has the most accurate heart rate monitor? In this guide, we will list smartwatches for tracking heart rate (in no order of favouritism). There’s nothing too scientific about our recommendations, just what we have observed. We’ve tested hundreds of smartwatches and a handful stood out to us. Results vary though, and heart-rate tracking is never 100% accurate on the wrist. Chest straps are much better.
Polar Vantage M and V
If you want to get serious about heart-rate tracking, the Polar Vantage M and V both beat everything else for heart-rate tracking accuracy and ability. It even has a brilliant VO2 max estimate mode. We found in our tests the Vantage M was the fastest device to recognise a switch from sprint to jog and walk to run. It’s fast to detect changes in pulse and continually measures heart-rate so nothing is missed.
Like their flagship Vantage series, the M600 smartwatch uses Polar’s proprietary optical heart-rate sensors which are the best in the business. But unlike the Vantage M and V, the M600 runs Wear OS which is a huge plus. The M600 uses 6 LEDs to detect the blood pulsing through your veins and returns accurate, consistent results. Resting HR is on point and light exercise tracking is too, making this a top choice.
Apple Watch Series 4
The Apple Watch Series 4 delivers impressive heart-rate accuracy - we’re not including it for nothing. It’s one of the most consistent smartwatches out there because the optical sensors are built into a large glass plate that is slightly raised from the back plate. This ensures the sensors are always on your wrist no matter how loose the strap is. Two green LEDs are used here to detect the blood pulsing through your veins.
Suunto Spartan Sport Wrist HR
The Suunto Spartan Sport is no enigma. It’s for serious training where every heart beat matters. The heart-rate tracking is widely regarded as one of the best. It uses PerformTek biometric measurement technology, developed by Valencell, the same company behind the Scosche Rhythm+ (a very good heart-rate armband). On the wrist HR tracking is as good as it gets, and you can pair a Suunto Smart Sensor chest strap for even greater accuracy.
Huawei Watch 2
If you don’t want an Apple Watch, the best Wear OS alternative for heart-rate tracking is the Huawei Watch 2. The lugs are low and the optical plate large, so the watch is always in contact with your wrist. It’s comfortable to wear and returns accurate, consistent results just a few beats off from a chest strap during exercise. Don’t read too much into the reviews saying the HR tracking isn’t good, because it is.
Garmin Forerunner 235
If you do long-distance running, the Garmin Forerunner 235 is one of the best heart-rate tracking smartwatches out there. It isn’t any good for fast running or training because it gets confused by the jump from resting to high heart-rate but it’s incredibly accurate over prolonged exercise like a 5k run. You’ll find every optical heart-rate sensor gets confused by fast training. To avoid this, you’ll want a chest strap.
Garmin Forerunner 935
The Garmin Forerunner 935 is a good chunk more expensive than the 235 but some users report the heart-rate tracking is much better. It’s faster to respond to exercise changes and is less inclined to get confused about cadence (steps per minute). We’ve only played with the 935 for an hour or two and the resting heart-rate was spot on. For exercising, it is better than the 235 but not as good as the Vantage M or Suunto Spartan Sport.
Fitbit Charge 2
If you don’t fancy an out-and-out smartwatch, the Fitbit Charge 2 is a more fitness focused device. It’s a fitness band with an accurate optical heart-rate sensor which automatically tracks heart-rate with good resting results -- so long as it is fitted tight to your wrist. The accuracy of heart-rate tracking is good when at rest but there can be issues when training, with the Charge 2 having a tendency to underestimate heart-rate.
Want to get serious about heart-rate tracking?
We’ll end our guide with some friendly advice. Wrist-based heart-rate trackers, be them smartwatches or fitness bands, are limited in their ability. Movement can throw tracking off which means they are not ideal for exercise. If you want the best smartwatch for heart rate tracking, the Polar and Suunto options listed are what we recommend above all else, but nothing can replace the chest straps available from the same brands. The Suunto Dual Belt is a very good chest strap which is affordably priced if you want to try that route.