How much sleep you need
Most adults do best on 7 to 9 hours, but needs differ. Pajdo estimates yours from your own nights and keeps it within that range.
Sleep experts give a range, not one magic number. The American Academy of Sleep Medicine and Sleep Research Society recommend at least 7 hours a night for adults. The National Sleep Foundation recommends 7–9 hours for adults 18 to 64 and 7–8 from 65, and notes some people do well at the lower end while others need every minute of the upper end.
Pajdo estimates your need from the median night of your last 60 days, naps included, once he has 14 nights. He keeps it between 7 and 9 hours, so if you've been running short for months, you're still measured against 7 rather than your current habit.
Sleep debt is the shortfall over your last 7 nights against that need. A long night pays back a short one in the same week, it never drops below zero, and nights without data add nothing. It's an estimate built on watch-tracked sleep, so read it as a rough gauge.
It's worth a glance, though. In a lab study, people who got 6 hours in bed a night for two weeks slipped steadily on tests of alertness and thinking while feeling only a little sleepier.
Worth a try
Keep your sleep times steady
The NHS says going to bed and getting up at similar times each day makes it easier to fall asleep. The American Academy of Sleep Medicine suggests getting up at the same time every day, even on weekends. A National Sleep Foundation expert panel agreed that regular sleep timing matters for health and performance.
Pajdo's bedtime consistency shows how much your bedtime has moved around over the last week, using sleep from Apple Health.
Try it: pick a wake-up time you can keep all week, set an alarm, and let bedtime settle around it.
Keep reading
Sources
- Recommended amount of sleep for a healthy adult: a joint consensus statement of the AASM and Sleep Research Society, Sleep (Watson et al. 2015)
- National Sleep Foundation's updated sleep duration recommendations: final report, Sleep Health (Hirshkowitz et al. 2015)
- How much sleep do you really need?, National Sleep Foundation
- The cumulative cost of additional wakefulness: dose-response effects of chronic sleep restriction and total sleep deprivation, Sleep (Van Dongen et al. 2003)
- The accuracy of Apple Watch measurements: a living systematic review and meta-analysis, npj Digital Medicine (Lambe et al. 2026)
- How to fall asleep faster and sleep better, NHS Every Mind Matters
- Healthy Sleep Habits, American Academy of Sleep Medicine
- The importance of sleep regularity: a consensus statement of the National Sleep Foundation (Sletten et al. 2023), Sleep Health
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.