Sleep consistency
How closely your sleep and wake times repeat from day to day.
- Poor0-69%
- Sufficient70-79%
- Optimal80-100%
What goes in
- Sleep sessions
- Main sleeps and naps, minute by minute.
- Band wear
- A day counts only if the band recorded heart rate for at least half of it.
How it is weighted
Pulse splits the last 7 noon-to-noon days into minutes, each asleep or awake, and checks each minute against the same minute the next day. The Sleep Regularity Index (Phillips 2017) is −100 + 200 × the share that match: 100 means an identical schedule, around 0 a random one. Pulse shows it from 0 to 100%, with anything below zero as 0%. A 1-hour nap lowers it by about 3 points.
It makes up 10% of Sleep Performance and is one of the inputs to Pulse Age.
What the bands mean
- 80-100%
- Optimal
- 70-79%
- Sufficient
- 0-69%
- Poor
Limits
It needs 2 worn days in a row within the window; otherwise there is no value. Days without the band are skipped rather than counted as awake. Fitbit’s sleep sessions leave out brief wakes, so this reads somewhat higher than a lab measure. On the night the clocks change, times are compared 1 hour apart.
Sources
The full specification, with formulas, constants and worked examples, is sleep-regularity.md on GitHub. The code is tested against those examples.