Sleep Calculator
Wake up refreshed. Enter the time you need to wake up and find the best bedtimes, based on 90-minute sleep cycles.
Sleep Calculator
The best times to go to bed and wake up, based on sleep cycles.
For a full night’s sleep, including 15 minutes to fall asleep.
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How to use this calculator
Enter the time you need to wake up, then press Calculate. You will see the best bedtimes for 6, 5, 4 or 3 complete sleep cycles. Aim for 5 or 6 cycles (7.5 or 9 hours) for a full night’s rest.
Formula
Each sleep cycle lasts about 90 minutes, and most people take around 15 minutes to fall asleep. Waking at the end of a cycle — rather than in the middle of one — feels much more refreshing.
Frequently asked questions
How many sleep cycles do I need?
Most adults need 5 or 6 cycles — 7.5 to 9 hours of sleep. Some people feel fine on 4 cycles occasionally, but regular short sleep harms health.
Why 90 minutes per cycle?
Sleep runs in cycles of roughly 90 minutes, moving through light sleep, deep sleep and REM sleep. Waking between cycles avoids grogginess.
What if I go to bed later than the suggested time?
Pick the next suggested bedtime for fewer cycles — it is still better to wake at the end of a cycle than in the middle of one.