Apple Health metrics › Core Sleep

Core Sleep on Apple Watch and iPhone

Time in light-to-moderate sleep, which makes up the largest share of the night.

What it is

Apple Health groups the light stages as Core sleep. It is the bulk of your night and supports memory and general recovery.

How Apple measures it

Apple Watch estimates the stage from motion and heart rate patterns.

What's a normal range?

Core sleep is typically around 45 to 55% of the night.

What moves it

• Total sleep time
• Stage mix shifts with age
• Alcohol and late meals
• Temperature
• Training load

See Core Sleep next to your other vitals

Apple Health keeps this number several taps deep. OnlyVitals puts the metrics you pick, including Core Sleep, on a single dashboard so you can read them at a glance. Everything stays on your device.

Frequently asked questions

What is Core sleep on Apple Watch?

Apple's name for the light, non-REM, non-deep stages (roughly stages 1 and 2). It is normally the largest block of the night.

Is a high Core sleep percentage bad?

Not by itself. Look at total sleep plus Deep and REM too, and track your own average.

Related metrics

• Awake Time During Sleep
• Wrist Temperature
• Walking Heart Rate Average
• Heart Rate Recovery
• Heart Rate
• Walking Speed

This page is general information, not medical advice. Ranges vary by age, sex, fitness and device. Talk to a clinician about anything that worries you.