The Data Is In: How Accurate is the Apple Watch Heart Rate Monitor?

The emergence of the Apple Watch – the first smartwatch delivered by Apple – has thrown the fit-tech space on its head. Overnight the space has transformed from a landscape filled with a raft of highly competitive, sport specific tech brands like Fitbit to a marketplace that is quickly been sewn up by the global household player that is Apple. This raises questions though for all fitness buffs out there. How accurate is the Apple Watch as a heart rate monitor compared to dedicated heart rate monitors?

Many hard training athletes come to rely on the data that comes from their heart rate monitor. In fact, dedicated heart rate monitor users come to base their whole workout output on the data that their watch spits back at them, and a result, this is clearly of great performance of them. The data has to be as accurate as possible.

Quickly, an assumption has grown that the Apple watch will not be anywhere near as accurate as a sport specific offering. It’s been readily theorised that the Apple Watch is lightly touching the sport space, and that, at its heart, the Apple Watch is really a much more general offering. However, this is largely a misnomer, because sport and fitness was actually one of the core pillars that brought Apple to this party. One of the great criticisms of the smart watch space to date has been the lack of unique value (over and above your increasingly ever-present smartphone) that the device can bring. Its been readily accepted that sport and fitness is one such area where the watch can beat the phone, so naturally making the watch very good at the fitness side of things does actually make a lot of sense.

So the simple answer to the question ‘How accurate is the heart rate monitor on the Apple Watch?’ actually makes for surprisingly good reading. In short, it is as accurate as a dedicated wrist-worn heart rate monitor.

This is according to SonoPlot engineer Brad Larson who recently posted a chart on Twitter which clearly shows a comparison between the heart rate data from the Mio Alpha (a great example of one of these dedicated sport specific brands and offerings which have had their way with the fit-tech market to date).

In theory, the Mio should win. It’s considered a solid fitness technology offering – priced at $149 it is affordable yet expensive enough to carry a weighty spec verses the more basic fit-tech rival offerings. It pulls data in every three seconds, and on paper this batters the Apple Watch, which updates only every five seconds. When you consider this is the difference between collecting 20 data points per minute verses just twelve, you start to see the scale of data differential. Extrapolated over an hours run, this becomes 720 data points (Apple watch) verses 1,200 data points (Mio) – so we would expect a clear data difference. The undulations in workout intensity, the constant moving goal posts of your heart rate, and the general ebbs and flows of your bodily response to exercise dictates the importance of collecting as much data as possible. or so the logic went, because in actuality, both devices recorded near identical results.


Therefore, that becomes a clear 1-0 to the Apple Watch and its accuracy as a heart rate monitor. Add in its capabilities outside of sports and fitness, and we start to get a compelling picture of what Apple have brought to the table. Food for thought.