Which smartwatch brands are most accurate for heart rate? Plus tips to improve tracking

You’re out for a run, breathing hard, convinced you’re going at your limit. Then, you glance at your wrist. It says your heart rate is… just 80 bpm? We’ve all been there. You want to know if that number is real or just a random guess.

At Which?, we don’t just take the manufacturer's word for it. We’ve spent the last year running 58 different devices through our labs – from the latest Apple Watch devices to super cheap fitness trackers – comparing them against medical-grade chest straps. Here is what the numbers say.

Our fitness tracker reviews and smartwatch reviews include lab tests of all the most popular models. And check out our guide to the best smart rings to see if they're a better option.

Heart rate accuracy on smartwatches

We judge these trackers by looking at the error rate. In plain English, that just means checking how often the watch disagrees with a medical-grade chest strap. If the strap says 160bpm and the watch says 160bpm, that’s a perfect score.

The results this year have been close. But when we looked at the consistent performers over the last 24 months, some brands stood out from the rest.

It might be surprising to see Oppo at the top here – but this is based on only one review, the impressive Oppo Watch X2. 

It's perhaps not so surprising to see Apple placing strongly in second. Big brands like Samsung and Garmin are lower down, but ~2.3% is still a respectable score overall. These could also be suffering a bit from 'testing volume'; we have tested more of their models over the years.

You might be thinking, 'So what if it misses a beat or two? I’m not an Olympian.' But your heart rate is the foundation for many metrics that your watch tells you. If that number is wrong, the rest of the data is less reliable.

Take calories, your watch guesses how many calories you burn based on how hard your heart is working. If it thinks your pulse is racing when you are actually sitting on the sofa, it might tell you that you’ve burned off a burger when you haven't even burned off a biscuit. If you are trying to exercise smarter – like keeping your heart rate low to burn fat – an inaccurate watch could mislead you at a key time. You might think you are taking it easy, but your body is actually overtraining.

A sudden rise in your resting heart rate can be the first sign you are getting sick or stressed. If your watch is unreliable, you miss that early warning signal.

What's also notable from our table above is how brands differ based on heart rate during different types of exercise, which can be a good steer depending on what you do most often. So, which brand should you look out for?

• Oppo is the dark horse. If its Watch X2 is anything to go by from a brand perspective, it could be the one to watch, whether you’re walking the dog or sprinting.
• Apple is almost boringly consistent. It's delivering high-level accuracy, and performs better than Oppo at rest and when walking.
• The Google Pixel Watch range is solid, but it really shines when you aren't moving. It had the second best Resting Heart Rate accuracy (1.03%), just behind Polar (0.88%).

Find out more about how we test smartwatches

How to improve heart rate accuracy on a smartwatch

Before you go out and buy a new watch, try fixing the one you have. A lot of 'bad data' is actually just a bad fit.

• Position is everything. Most people wear their watch too low, right on the wrist bone. Slide it up your arm so it sits two finger-widths above the bone, ensuring the sensors lie flat against your skin. It should be snug but comfortable. If you are heading out for a run, tighten the strap by one extra notch. A loose watch bounces, and a bouncing watch guesses.
• Sensors struggle with two main things: cold skin and grime. If you have poor circulation or it’s a freezing morning, your blood vessels constrict, and the watch can’t "see" your pulse. Warm up for a few minutes to get the blood flowing before you start tracking. Sweat, sun cream, and dust can block the sensor’s light. Give the back of the watch a regular wipe (checking the manual for the best method) to keep the view clear.
• Sometimes a 'wrong' reading is actually right. Factors like smoking or drinking alcohol can temporarily spike your heart rate. If you see a high number after a glass of wine, it’s likely your body reacting, not a glitch. Try measuring again later to get your true resting baseline.

Read our guide on the best cheap smartwatches for more on choosing the top budget option. 

How does smartwatch accuracy compare to fitness trackers and smart rings?

We appreciate the appeal of smart rings. They are discreet, stylish, and comfortable to sleep in. But if you care about precise numbers, the technology has some catching up to do.

Now, we stand by our testing, but context is king. We have more data on smartwatches (over 80 reviews), which makes those averages very reliable. For smart rings and fitness trackers, our sample size is smaller – around 4 and 15 models, respectively.

That means one poor performance from a single ring model can drag down the average for the whole category more than it would for a smartwatch brand. As we test more rings in 2026, we expect these numbers to settle. But for now? Treat the ring data as a guide, not a guarantee.

The 20.2% error rate for resting heart rate is notable. If you want a ring, get one for the general health trends. If you want more precision, stick to a watch.

Looking to track more than just heart rate? Take a look at our guide on how to track sleep on your smartwatch or fitness tracker