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Sleep Calculator
Work out the best time to go to sleep or wake up based on 90-minute sleep cycles, so you wake between cycles feeling refreshed instead of groggy.
I want to wake up at…
I’m going to bed at…
About Sleep Calculator
Sleep happens in cycles of roughly 90 minutes, and waking at the end of a cycle — rather than the middle — helps you feel rested. Tell the calculator when you need to wake up and it suggests bedtimes that complete whole cycles (allowing about 14 minutes to fall asleep). Or tell it when you are going to bed and it suggests the best alarm times. Aim for five to six complete cycles, about 7.5–9 hours, a night.