Metric

Sleep

What your sleep score is built from, why it moves, and what the stages and totals actually mean.

Sleep scores feel precise, but they're built from estimates, and they don't always match how rested you feel. A good night can score badly and a short night can score well. Here's what the research says these numbers are really tracking, what moves them, and how much weight to put on the score versus the trend.

The benchmark
Sleep
Sleep Score Explained: What Is a Good Sleep Score?

What goes into the number and what it can and can't tell you.

See how you compare
Example result
Age 40 ยท 6.5 h
just below the recommended range
NSF expert consensus
Research Desk · live file
See the full Sleep evidence file
Every claim rated Established, Emerging, Uncertain, Insufficient, or Unsupported, with a research log reviewed against new studies on a rolling basis.
Open the Research Desk →
More on Sleep
What Is REM Sleep, and What Does Your Tracker's Number Mean?
Your wearable reports a REM percentage every morning, but the science behind that number is more complicated than the readout suggests.
How Much Deep Sleep Do You Need?
The number on your wrist lands somewhere between 30 and 90 minutes for most adults, and the research explains why that range is real, not a glitch.
Does Poor Sleep Actually Raise Dementia Risk?
Wearables report a deep-sleep percentage, but the research behind that number points somewhere more consequential than next-day grogginess.
How Consumer Wearables Infer Sleep Stages
Movement sensors and heart rate proxies can approximate your sleep architecture, but the gap between a wrist device and a full lab study is measurable and documented.
Other metrics
Heart Rate Variability Resting Heart Rate Sleep VO2 Max