Sleep Cycle Calculator
Calculate the best times to wake up or go to bed based on 90-minute sleep cycles. Avoid waking up mid-cycle to feel more rested.
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Frequently asked
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A sleep cycle is approximately 90 minutes long and consists of several stages: light sleep (N1/N2), deep sleep (N3/slow-wave), and REM sleep. A full night of 7–9 hours typically includes 5–6 cycles.
Waking up in the middle of deep sleep causes "sleep inertia" — the groggy, disoriented feeling that makes mornings difficult. Waking up at the end of a cycle, during lighter sleep, makes you feel more alert.
The average person takes about 10–20 minutes to fall asleep. This calculator uses 14 minutes as the default, but you can adjust it.
Adults need 7–9 hours (about 5–6 sleep cycles). Teenagers need 8–10 hours, and children need 9–12 hours. This calculator shows optimal options within these ranges.