bitshealth

How accurate is sleep tracking, really?

No wearable can see brain waves. Here is what we can measure well, and what we show with honest uncertainty.

By the bitshealth team. Published July 21, 2026. 6 minute read.

A sleep lab records brain waves, eye movement and muscle tone to decide what stage you are in. A wearable has heart rate, movement and breathing. It is inferring, and the best devices are good at it, but it is still inference.

What we measure well

Total sleep time, time to fall asleep, and long awakenings are reliable enough to act on. These are the numbers the app leads with.

What we show with care

Deep and REM minutes are estimates. In the app they appear as ranges, not exact counts, and we never build your readiness score mainly on them.

What actually moves the needle

Consistent bed and wake times change your sleep more than anything else. If you find the score making you anxious, you can hide it and keep only duration and consistency.

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