How accurate are wrist-based HR monitors?

I have a FitBit Blaze, and it tends not to be very accurate compared to a chest strap when doing sudden changes in load. In today’s Kaweah for example, during the warmup ramp the FitBit read >170 when the cheststrap was still below 120 BPM.

One answer is a ‘better’ wrist strap, but I wonder how accurate measuring HR at the wrist with optical technology is relative to measuring it at the chest with a strap. Is there any data on this?

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I think the optical HR monitors (wrist and phone etc) accuracy really seems to vary person to person. For me they seem very accurate. For my wife - random number!!!

My go-to person for this is, and he consistently finds wrist based devices struggle with cycling, presumably because of the bending of the wrist. I have a Polar M430 watch and it’s hopeless on the bike, indoors and out. Other optical devices worn higher up the arm are generally good though.

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I’ve used the Strava app on my Apple watch when out on my mtb. It’s absolutely rubbish as a HRM.

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I don’t use the wrist HR on my Garmin Fenix 5 at all anymore, when I need an accurate measurement. It has been useless anywhere I’ve tried using it, gym, bike etc.

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Garmin f35 generally fine, save for the odd max blip. Swimming however is practiacally useless

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I use a Garmin 735xt and it’s generally great for me, responding well to effort changes even short efforts like strides or bike sprints.

I do however think it’s as much to do with the person wearing it as the device itself. Someone I train with also uses a 735 and he’s often complaining about it’s inaccuracies.

I have a garmin 935 and the ohr works pretty good for steady state runs. For intervals it does ok which I am probably the minority and for me ohr has been acceptable.

Anything like cycling / lifting where your wrist blood flow is restricted it can have some funny readings. This is why when I am doing those I wear a hrm if I want accurate readings.

ECG HRM are more accurate and less laggy than PPG HRM. The darker your skin is, the more this will be true.

If you have a super light complexion and take special care to eliminate background noise (extraneous light) then, good news, PPG will probably work well for you.

My personal experience is that my garmin HRM strap, as reported on my garmin GPS device, correlates very well with medical grade heart rate monitoring devices. (The things we do to while away the hours in the hospital!) However, my experience with wrist worn PPG devices is that they do NOT correlate well with my garmin HRM strap. PPG devices are regularly off by 15+ BPM. So that is one person’s experience.

I’ve never seen anyone with a wrist-based HR monitor get accurate readings.

If you’re serious about tracking HR I’d say just buy a HR strap.

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I’ve used Apple watch for years. At first I was worried about accuracy, so I did a few runs/rides wearing the AW and my old Polar with chest strap.

The readings matched.

All HR devices make errors, the benefit of the Health app is that you can see every record and delete out that sudden crazy high/low number that pops in occasionally. Personally I just glance at the graph at the end of a Workout and mentally edit I’d I need to. Really I just want to know what zone I was in, so I don’t need hyper precision/accuracy.

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I seem to think in the last few weeks dcrainmaker suggested the latest Apple Watch was the best wrist based optical device. Should be in his latest guides.

I have used a Mio Velo for years and have no complaints about it’s accuracy. I wear it as they suggest for cycling - with the sensor on the inside of the wrist. I tested it against my chest strap monitor and received very similar values. Unfortunately, Mio has dropped out of the hardware business but the devices are still available online.


”And yup, for now I’d pretty easily give Apple the award for the most accurate wrist-based optical HR sensor out there today.”


I own and use chest, wrist and forearm HRMs. I can say getting a dedicated HRM is better than any watch based activity tracker HRM. I currently own MIO VELO(wrist), Scosche Rhythm+ (forearm) and Garmin (Chest) , they are all very accurate in my opinion. I also use a Garmin Vivoactive HR, which is not as accurate as the others( Not even close, in my mini comparison, it had my HR up are high as 202 on a ride). The Velo and Rhythm+ are both ANT+ and BLUETOOTH.

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Simple answer to your question: wirst based hr sensor are not accurate.


I’ve said it on here before, always have problems with HR straps to the point I believe my Apple Watch way more.
I’ve used polar, Garmin and Wahoo straps, all seem to work fine when new but soon deteriorate. I hand wash after workouts but doesn’t seem to help. Been suggested I use gel but not got round to buying any yet.
On yesterday’s ride right from the door my Wahoo hr strap read 170bpm and didn’t budge for 40 minutes! I eventually thought I’d stop and try fix it, undid the strap until reading dropped. As soon as I attached the center piece to one side of strap, bang 170bpm again - I’d not even connected it to both ends let alone got it across my chest for gel to help! I’ve changed the battery ahead of tomorrow’s workout to see if it helps - the Wahoo app said battery was 20% so would expect it to still be working to be honest. If it’s still no better I give up and will just ditch recording he - it’s more hassle than it’s worth!

My first Garmin premium HR strap stopped working after 16 months, since then I basically follow Garmin’s advice (hand wash every use, and toss in with cycling kits once a week). My Wahoo TickrX strap is still going strong after something like 4 years. My Series 4 Apple Watch is surprisingly accurate, once switched to workout mode, but I have caught it “stuck” a couple of time while at rest. I’ve got what seems to be a lifetime supply of electrode gel, I only need to use it a couple times a year. I’ll go look for it and let you know, think there are 4 tubes of it in the garage.

New battery in tickr, sat at 137bpm for maybe 5 mins then seemed to jump into life and dropped to pretty much match my Apple Watch which I felt was accurate. Will see what the mornings workout brings.

Regarding gel, I’m in the UK so don’t go raiding the garage on my behalf, thanks all the same!

Garmin 235 is ok, for running, but the wrist angle cycling means I can’t get a decent ‘seal’ and signal. I use chest strap as well. Even with running it sometimes takes a while to get it’s head around where I am rate wise. I think it uses cadence to help judge effort when not sure (ie at beginning).
It’s ok for daytime HR monitoring, but I dont think it’s accurate enough for exercise monitoring for me.