Sleep efficiency
The share of your recorded sleep time that you actually spent asleep. Higher means less time lying awake.
Pajdo divides the minutes you were asleep by all the minutes your sleep data in Apple Health covers that night, awake bits included, and shows it as a percentage.
The number depends on what's recording. Apple Watch only logs awake time that falls between two stretches of sleep, so the time it takes you to drift off isn't in it unless another app records your time in bed. The watch also marks some real awake time as sleep. Both push a watch-only number up, so read it as a trend line rather than a lab result.
The National Sleep Foundation's sleep quality checklist asks adults of every age whether they were asleep for about 7 of every 8 hours in bed. Caffeine is a reliable dent: in a review of 24 studies it lowered sleep efficiency by 7% on average. Regular exercise lifts it a little.
What tends to push it up
- Regular exercise, by a little
What tends to pull it down
- Caffeine later in the day
- Long awake spells in the night
Worth a try
Make your bedroom cool and dark
The NHS, the American Academy of Sleep Medicine and the National Sleep Foundation all point the same way: a bedroom that's quiet, dark and comfortably cool. The NSF notes the best temperature differs from person to person.
Small fixes go a long way. Blackout curtains or an eye mask for light, earplugs or gentle background sound for noise.
Try it: tonight, close the curtains fully, turn your phone face down on silent, and make the room a touch cooler than usual. Tweak one thing at a time until it feels right.
Keep reading
Sources
- HKCategoryValueSleepAnalysis, Apple Developer Documentation
- Estimating Sleep Stages from Apple Watch, Apple (updated October 2025)
- What Is Sleep Quality?, National Sleep Foundation
- The effect of caffeine on subsequent sleep: a systematic review and meta-analysis, Sleep Medicine Reviews (Gardiner et al., 2023)
- The effects of physical activity on sleep: a meta-analytic review, Journal of Behavioral Medicine (Kredlow et al., 2015)
- How to fall asleep faster and sleep better, NHS Every Mind Matters
- Healthy Sleep Habits, American Academy of Sleep Medicine
- How to Make a Sleep-Friendly Bedroom, National Sleep Foundation
Checked against these sources on September 15, 2026.
This is general wellness information, not medical advice. If a number worries you, or stays away from your usual for a while, talk to a doctor.