Sleep Calculator
Wake up refreshed, not groggy. Pick a wake time or bedtime and get the optimal sleep and wake windows aligned to 90-minute sleep cycles.
Go to bed at one of these times to wake up feeling refreshed:
How sleep cycles work
Each sleep cycle lasts about 90 minutes and moves through light sleep, deep sleep, and REM. Waking up at the end of a cycle — rather than in the middle — is what leaves you feeling alert instead of groggy. This calculator adds 15 minutes to account for the average time it takes to fall asleep.
Recommended hours by age (NSF)
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