Smart watch metrics - how accurate are they?

May 31, 2023


I was curious about how accurate my apple watch is, so I did some digging and found this video:

In this, they try out four devices: Apple watch, Mi Band, Fitbit, and a phone in hand.

It's worth watching in full, but here's a summary:

  1. Steps
    • In general Apple watch is close. Phone does the best
    • If your hand is fully steady, Apple watch counts 0 (in the video he's carrying a glass of water). Fitbit and the phone do better.
    • Apple watch does better when you are walking weirdly too. Fitbit/mi band and phone all overcount in these cases.
    • Fitbit overcounts a lot. For eg, in this video, it counts steps even when driving.
  2. Heart rate
    • Benchmarked against an electric measure strapped to the chest.
    • While running
      • All of them mostly do good, except in extreme cases (sudden change in running pace for example).
      • In the case of a sudden increase, Apple watch comes the closest to real heart rate.
    • Throughout the day
      • Apple watch's frequency of recording is 4 minutes, compared to Fitbit's 8 seconds & Mi Band's one minute. This means that Apple watch misses a lot of cases.
      • Mi band is the least accurate.
    • Sleep tracking
      • All watches work well in this case, as conditions are ideal. Avg error is 1.8 bpm for Apple & Fitbit, 3.4 for Mi band