GlenCalc

Sleep calculator

Sleep runs in cycles of roughly 90 minutes. Waking at the end of a cycle tends to feel easier than waking in the middle of one.

Your answer

Go to bed at9:15 PM9 hours of sleep: 6 cycles
Other good bedtimes10:45 PM (5 cycles, 7.5 h); 12:15 AM (4 cycles, 6 h)

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How we worked it out

Updated as you change the numbers.

  1. Bedtime = wake time − (cycles × 90 min) − time to fall asleep. Wake time = bedtime + time to fall asleep + cycles × 90 min.

Method and assumptions

Cycles average about 90 minutes but vary from roughly 70 to 120 minutes between people and through the night, so treat these times as starting points. Adults are generally advised to get at least 7 hours of sleep a night.

Questions

When should I go to bed to wake up at 6:30 AM?

About 9:15 PM for six cycles, or 10:45 PM for five.

Sources

Method and figures checked on . Every worked answer on this page is covered by an automated test. Found a mistake? Tell us.

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