Waking up at the end of a sleep cycle, rather than in the middle of deep sleep, helps you feel less groggy. Choose whether you know your wake-up time or your bedtime.
Best times
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This calculator gives a general estimate for adults and is not medical advice. Talk to a doctor or a registered dietitian before making health decisions.
Sleep runs in cycles of roughly 90 minutes, moving from light sleep to deep sleep and REM sleep. Most adults need five or six cycles — 7.5 to 9 hours — a night.
The calculator counts back (or forward) in 90-minute steps from your chosen time and adds 15 minutes for falling asleep. Cycle length varies between people, so use the times as a guide.
Most adults need 7–9 hours. Teenagers need 8–10 hours and older adults 7–8.
You may be waking in the middle of a deep-sleep phase, or sleep quality may be poor. A regular schedule, a dark cool room and less caffeine late in the day all help.