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Sleep Calculator

Find the best bedtime or wake time based on 90-minute sleep cycles. Wake between cycles to feel more refreshed.

HealthWellness
Mode

Go to sleep at

6 cycles
21:45
9 hours of sleep
5 cycles
23:15
7.5 hours of sleep
4 cycles
00:45
6 hours of sleep
3 cycles
02:15
4.5 hours of sleep

What is a sleep cycle?

A sleep cycle lasts roughly 90 minutes and includes stages of light sleep, deep sleep, and REM sleep. Waking between cycles rather than mid-cycle helps you feel more refreshed. Most people go through several complete cycles each night.

Why does it add 15 minutes?

The average adult takes about 10 to 20 minutes to fall asleep. The calculator adds 15 minutes to account for this, so the suggested bedtime gives you time to drift off naturally before your first sleep cycle begins.

How many sleep cycles do I need?

Most adults need 5 to 6 complete cycles (7.5 to 9 hours) per night. Four cycles (6 hours) is the minimum for functioning, though not ideal long-term. The calculator highlights 5 and 6 cycle options as the recommended choices.

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