Samsung smartwatch heart monitors are inaccurate and inflated, our testing confirms

I'm not a fitness freak by any stretch of the imagination, but I am concerned about my health. I'm not an athlete, so I don't own a Garmin, or a Polar heart rate monitor, and like many New Year's resolutions, my goal this year is to work on my cardio and general fitness with whatever tech I have to hand that can help. Furthermore, I have hypertension and a history of heart attacks in my family, so at ripe old middle age, it's probably about time I started looking after myself. My guide on this journey is my 3-year-old Galaxy Watch 4, where I am keen to use the heart rate zone feature to be able to consistently keep my heart rate in the cardio zone as I pedal away on my spinning bike, while watching episodes of Silo.

There are many things that can impact the accuracy of a smartwatch heart rate sensor. Body hair, fat, tattoos, skin colour, positioning and strap tightness to list but a few. I'm pretty sure I've got all of these covered, so I was surprised when my Galaxy Watch 4 would report a heart rate in the 80's when sitting on the sofa and would regularly bump up against the maximum 174 beats per minute (BPM) for my age when doing vigorous (but not that vigorous) exercise. I'm unfit, sure. But I'm not massively overweight, and I do a reasonable amount of walking and other activities outdoors.

That got me thinking, I place so much faith in my smartwatch to be accurate, is my faith misplaced?

I don't have access to a range of medical grade equipment, but I do have a clinically validated Omron HEM-7120 blood pressure monitor that also measures heart rate, an exercise bike with a heart rate monitor and a Galaxy Watch 5 for comparison. With my wife on standby with the camera, it's time to compare.

I took my first reading on the sofa, although having just put the children to bed, this wouldn't be my normal resting heart rate. Nevertheless, there is only 1 BPM between the three devices, so in this case the reading on both Galaxy watches seems to be relatively accurate.

Following the initial reading, the warm-up begins, aiming to get my heart rate into zone 3 for the optimum cardio workout. After about 10 minutes the Galaxy Watch 4 shows me slap bang in the middle of zone 3, but displays a heart rate of 146. The zone 3 range should be somewhere between 122 and 139 beats per minute. Perhaps it takes time to update? The Galaxy Watch 5 on the other wrist shows a very similar heart rate, but at least has the zone right, as I am clearly in zone 4 if the numbers are to be believed.

I already had the Omron strapped to my arm, so took a reading with that, as well as the bike heart rate monitor. However, the Omron reported a heart rate of only 115 BPM, putting me in the middle of the "weight control" zone according to Samsung's numbers. Multiple tests with the Omron achieved a similar result, although the 3rd test resulted in a somewhat higher 121 beats per minute, as seen in the photo, still nowhere near either Galaxy Watch. The bike's built in heart rate monitor was even lower, but I'll chalk that one up to a cheap sensor that probably wasn't that reliable to begin with.

After another 10 minutes and definitely getting a sweat on, I took another reading on the Omron. The gap is somewhat narrower, but there is still a good 5 BPM difference between the Galaxy Watch and the Omron.

I'm not a scientist, and this was in no way a scientific test. But these are the devices the average consumer likely has access to, and at the end of the day, Galaxy Watches are a product the average consumer is likely to buy. So what are the takeaways from this experiment?

The first thing I can say for sure is that the heart rate monitor built into the bike is garbage. The second thing I can say with some certainty is that the heart rate monitor on both the Galaxy Watch 4 and 5 is probably more of a guide than an accurate representation of your heart's activity. Maybe the average person only needs a guide, or maybe Samsung overestimates the average person's heart rate so they don't overexert and end up doing some damage, landing a lawsuit squarely in Samsung's lap.

Either way, Reddit r/GalaxyWatch is filled with threads about inaccurate or overestimated heart rate measurements for the Galaxy Watch 4, 5, 6 and 7.

I really hope Samsung fixes this issue with its next iteration. However, based on their track record, consumers looking to accurately measure heart rate and heart rate zones should probably look elsewhere. If you can't trust the heart rate readings on your smartwatch, how can you accurately trust it to track your health? I'm not even going to mention their blood pressure monitoring, and the fact that some features already have FDA approval seems outright laughable.

My last certainty from this experiment is that my next smartwatch purchase will probably be a Garmin Venu 3 (Available on Amazon), followed by a trip to get my blood pressure checked.