Bedtime calculator
Waking up mid-cycle is what makes some 8-hour nights feel worse than good 7.5-hour ones. Sleep runs in roughly 90-minute cycles, so the trick is to time your bedtime — or your alarm — to land between cycles, not in the middle of one.
Go to bed at…
Falling asleep now instead?
If you're in bed already, aim for one of these alarms:
How it works
The math is simple: your wake-up time, minus a whole number of 90-minute cycles, minus the time it takes you to fall asleep (about 15 minutes for most people). Five to six cycles — 7.5 to 9 hours — is the range most adults do best on.
Ninety minutes is an average, not a law: real cycles run 80–110 minutes and drift through the night. Treat the suggestions as good anchors, and adjust by how you actually feel in the morning. If you're consistently exhausted despite enough hours, that's a conversation for a doctor, not a calculator.
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