Heart rate monitors (watch) - British Heart Fou...

British Heart Foundation

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Heart rate monitors (watch)


Just wondering how accurate heart rate monitors on devices like Apple Watch or Fitbit or the likes. Would love to know others thoughts on this.

23 Replies

My fitbit often tell me my HR is in the 50's when it's actually in the 70's. I also manage to achieve 10000 steps as a passenger in a car!! I still wear it as a gauge to ensure I'm getting enough steps by comparing it to previous days steps but it's by no means accurate.

Amok0310 in reply to Lezzers

Mine is the Apple Watch as I gave up on the Fitbit as the readings were very random. I’ve started to check my BP regularly (as requested by my GP) which also shows heart rate and up to now it matches the readings on my watch. I guess I’m just sceptical after the issues with my Fitbit.

Lezzers in reply to Amok0310

I have heard good and bad bout the apple watches, I think some are accurate and some are not, luck of the draw? My husband has to monitor his BP as asked by cardiologist and GP and his nurse gave him the NHS BP monitor that she uses and that are used in hospitals the monitor also shows the HR. However, interestingly when his nurse was taking his BP she always did the finger on pulse for the heart rate which they also do in the hospital, makes you wonder!!


I have the Apple Watch 4 and I think it’s pretty accurate, I had a 24 ECG which showed lowest HR 40 and highest 145 and it matched with my watch!

Amok0310 in reply to Hidden

I have the 4 too. My GP advised I should stick with it as his opinion is they are pretty accurate. I guess I’m maybe hoping that my HR doesn’t actually drop as low as it shows and the watch is wrong. Got a first appointment with a Cardiologist in November so I’m sure all will be revealed.

Hidden in reply to Amok0310

Yes I think they are as well I looked at loads of reviews before purchasing just to make sure! I’m actually having an ecg today and booked in for another 24 hour ecg next week because I’ve been experiencing low HR in 40s which the watch has picked up on! so it will be interesting to see! Good luck, I hope they get to the bottom of it! Have you had any monitoring for your HR from your GP?

Amok0310 in reply to Hidden

I had an ECG at my doctors surgery and apparently the heartbeat looked fine but there was a concern that there were depressions showing in V2 and V3. All new to me really as I only highlighted it to my GP after noticing dips to around 40-45 about 3 times a day. The lowest it has been is 32 but mainly drops to 40s. Looking back over the history on my health app it’s been going on since 2016 (that’s when I had my first Apple Watch). A family member in the medical profession noticed it and said I needed to see my GP. Obviously once it came to light I looked back over the history.

Hope all goes well with your ECG

MichaelJHHeart Star

I use the step counter on my phone but comparing with a friend's watch I do half their steps! Now whilst they are over half a foot shorter their stride is not half mine as arthritis limits mine. Manual counting suggests my phone is accurate apart from stairs!

I will be buying a BP monitor as some readings suggest I may be over medicated - 105/51!

102/60 is about normal for me in the mornings but scored 86/55 (symptom free) this morning. Assumed bad reading, so took it twice more over 10 minutes with the same result.

Probably should have a word with the doc :)

I have a Xiaomi Mi Band 3 which is remarkably accurate when compared to the Polar chest strap monitor I use in the gym. Happen to have them both on at the moment (gym this afternoon) and the readings sitting in work are Polar: 63 Mi Band:64.

Unlike a lot of wrist monitors, it also manages remarkably well when exercising. On a 3.5 mile run / walk on Saturday the Polar showed a peak of 157, the Mi Band registered 155.

It's missing some of the bells & whistles of the better known brands, like GPS, 50 gazillion sports to chose from, and HRV measurements, but in return for that it lasts a comfortable 2 weeks or more between charges and only cost about £25 on Amazon.

The display is lousy in bright light but apparently they've improved that a lot on the Band 4.

Just rechecked after typing this, Polar says 65, Band says 66. Not bad!

Hi - they're not very accurate (see theverge.com/2016/10/13/132...) - research published in 2016 so things might have improved since then) at higher levels but the Apple Watch is the most accurate. They work by shining an LED onto the capillaries on your wrist and then measuring their expansion/contraction as blood flows through them. They're not as accurate as the monitors that you can fix to your chest and I imagine it's easier for devices placed on a finger to spot capillary changes than on the wrist.

At Cardio rehab we were advised not to use them for exercise purposes if the intention was to achieve a target heart rate. The advice was to use the Borg Rating of Perceived Exertion (en.wikipedia.org/wiki/Ratin...) and not to go above 'Hard'. There were many reasons for this advice (as far as I can remember) that mainly had to do with the effects of different medications (betablockers etc) on the heart at different times of day.

I still use mine though. But mainly to see how I'm progressing while I'm exercising (not to set a target) and to see when I've cooled down.

Hope that helps. And good luck!

I was using mine mainly for the gym and just to record exercise and steps and such. It’s just when all this came to light I was wondering how accurate they are.

I think they’re especially inaccurate as to steps - especially when not combined with distance tracking via GPS. They’re also bad at estimating calories. But even so - I still use mine!

Just back from a 75 minute session and the band shows a peak of 153 against 157 from the Polar.

Bear in mind that the chest strap reads every second but I've got the band set to take one reading every 5 minutes to save battery ( so brief spikes may not be caught), and that's pretty impressive from something reading by light through your skin!

One thing to be aware of with the Xiaomi is that their software rejects readings below 47 so, if you're looking for serious bradycardia it's not much use.

As for steps, on a walk yesterday over the sand dunes, the band registered 4832 steps while my phone (Google Fit) said 5135. Given the terrain I reckon that's pretty good agreement over 4km!

I have an Apple4 watch, it’s quite accurate for HR and I like it as it automatically goes to my phone. HR goes from 41 to 113!

Also should you be unlucky to have a fall it will call the emergency services if you don’t respond.

I don’t use it for exercise or anything like that, I don’t need to be told I’m not this that or the other.


Hi, my husband and I have Fitbits (Charge 2 HR). They both match the heart rate on our BP machine, which matches the BP machines at the GPs.

My garmin watch just told me my heart rate was 158 but my heart rate was actually 90

I almost threw it in the trash. I want a watch that can give me a more accurate reading

Amok0310 in reply to Aliciar

My Apple Watch seems to match up with my BP machine which is encouraging. I did have a Fitbit but that was giving really random readings hence swapping to the watch.

Aliciar in reply to Amok0310

I might need to switch to the Apple Watch

Amok0310 in reply to Aliciar

Oh and the added bonus is I listen to all my music at the gym with it and Bluetooth earphones 😊


Just to add my experiences. I had a fitbit ionic. It proved to be so inaccurate that it was effectively useless. I changed to a Garmin Vivoactive 3. This is reasonably accurate when not exercising, but becomes unreliable when running, rowing etc. However if paired with a chest strap it is quite accurate - as far as I can tell. The results look sensible and there are no 'spikes'.

Looking at the various forums for fitness watches this seems to be a common pattern. Fitbits are generally unreliable. Others are unreliable during exercise unless paired with a chest strap.

I have a Garmin 920XT HRM and have always found this to be pretty accurate, even against the HRM machine I was connected to in hospital. This model uses the ANT+ chest strap which is more accurate.

My fitbit is one or two beats out to the ambulance Pulse Oximeter. My HR bounces from 40-154 throughout the day which is consistent with SVT and possibly Brugada?.. I just have to monitor the high ones. Which the alarm will go off if my heart stays up there.

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