Sleep Cycle Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles, so you wake up between cycles rather than mid-cycle.
Best options (5–6 cycles)
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4 cycles (6 hrs) —
5 cycles (7.5 hrs) —
6 cycles (9 hrs) —
A general guide based on average 90-minute cycles — individual cycle length varies by a few minutes.
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How it works
Sleep cycles average ~90 minutes; waking at a cycle boundary (not mid-cycle) feels more refreshingFrequently Asked Questions
How do sleep cycles work?
Sleep moves through roughly 90-minute cycles of light, deep and REM sleep. Waking up in the middle of a cycle (especially deep sleep) tends to feel groggy, while waking between cycles feels more refreshed — even with fewer total hours.
How many sleep cycles should I aim for?
5 cycles (about 7.5 hours) or 6 cycles (about 9 hours) are common targets for adults; fewer than 5 often leaves people under-rested. This calculator adds about 15 minutes to fall asleep on top of the cycle count.
Should I plan bedtime or wake time?
Either — pick a wake-up time to find good bedtimes, or pick a bedtime to find good wake-up times. Both directions use the same 90-minute cycle math.