Sleep calculator

Sleep runs in cycles of about 90 minutes, and waking at the end of a cycle rather than mid-cycle tends to feel less groggy. To wake at 7am, common bedtimes are about 9.46pm, 11.16pm or 12.46am, which give five or six complete cycles after roughly 14 minutes to fall asleep. Enter your wake-up time, or choose to sleep now, and the calculator shows the times that land you at the end of a cycle. These are planning figures, not a medical measurement.

Pick whether you want to set a wake-up time, set a bedtime, or sleep right now. The calculator allows about 14 minutes to drift off, then counts back or forward in 90-minute blocks so you wake between cycles.

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How this is worked out

Sleep runs in cycles of roughly 90 minutes. Waking at the end of a cycle, rather than in the middle of deep sleep, tends to feel less groggy.

cycle length = 90 minutes
fall-asleep allowance = 14 minutes
bedtime = wake time − (cycles × 90 minutes) − 14 minutes
we show the options for 6, 5 and 4 complete cycles (about 9, 7.5 and 6 hours of sleep)

The 90-minute cycle and the 14-minute average time to fall asleep are widely used planning figures, not a medical measurement: real sleep varies by person and night. This is general information, not medical advice.

Looking for other time tools? Try the full set of calculators or the time-zone meeting planner.

The 90-minute sleep cycle and the average time to fall asleep are widely used planning figures. This is general information, not medical advice.