Sleep calculator
We count whole sleep cycles of 90 minutes (or the length you choose) back from your wake-up time, or forward from your bedtime, and add the time you take to fall asleep (15 minutes by default). We show 3 to 6 cycles and mark the option closest to the middle of the recommended range for your age.
Why 90 minutes? Sleep laboratory studies going back to the 1960s find adult sleep cycles average about 90 minutes, with a normal range of about 70 to 110 minutes. The first and last cycles of the night are often shorter than the middle ones.
Why 15 minutes to fall asleep? The National Sleep Foundation’s sleep quality panel rated falling asleep within 0 to 30 minutes as a sign of good sleep for adults, and most healthy adults fall asleep in 10 to 20 minutes.
Other calculators
- Nap calculator: 10, 20 and 90 minutes of sleep plus your time to fall asleep. Nap lengths are based on Brooks and Lack (2006) and the sleep cycle research above.
- Caffeine cut-off: caffeine left = amount × 0.5hours ÷ half-life. The cut-off is whichever is earlier: 6 hours before bed (Drake et al., 2013), or the point where less than 50 mg would remain at bedtime.
- Sleep debt: the sum of (need − hours slept) for each of the last 7 nights, counting only nights you slept less than you need. Recovery assumes up to 1 extra hour of sleep a night.
- Baby sleep schedule: total sleep from the AASM pediatric recommendations, with typical awake times and nap lengths for each age.
- Shift work planner: main sleep of 7.5 hours (5 cycles) starting 30 minutes after you get home from a night shift, a nap ending an hour before you leave, and caffeine stopped 6 hours before your main sleep.
- Jet lag planner: time zone differences from the official IANA time zone database in your browser, and adjustment rates of 1 hour a day eastward and 1.5 hours a day westward from the CDC Yellow Book.
Our editorial standards
Every page is written and checked by the BestTimeToSleep Team using published research and guidance from health bodies such as the American Academy of Sleep Medicine, the CDC and the National Sleep Foundation. We link to our sources so you can check them. We update pages when guidance changes. Our tools are for general information and are not a substitute for advice from a doctor.
Found an error? Please tell us.
Sources
- Watson NF et al. Recommended amount of sleep for a healthy adult. AASM and Sleep Research Society, Sleep, 2015
- Paruthi S et al. Recommended amount of sleep for pediatric populations. AASM, Journal of Clinical Sleep Medicine, 2016
- Hirshkowitz M et al. National Sleep Foundation’s sleep time duration recommendations. Sleep Health, 2015
- Centers for Disease Control and Prevention: About sleep (recommended hours by age)
- Feinberg I, Floyd TC. Systematic trends across the night in human sleep cycles. Psychophysiology, 1979
- Ohayon M et al. National Sleep Foundation’s sleep quality recommendations. Sleep Health, 2017
- Brooks A, Lack L. A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative? Sleep, 2006
- Drake C et al. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine, 2013
- CDC Yellow Book: Jet lag disorder
- Sleep Foundation: Shift work disorder