Sleep Cycle
Calculator
Every 90 minutes, your brain completes one full sleep cycle. Waking mid-cycle leaves you groggy. This calculator finds the windows where waking up is actually easy.
Free, no sign-up. Your numbers in, a clear target out.
Calculator
Find Your Sleep Windows
:
Go to bed at...
4 cycles · 6h
12:46 AM
5 cycles · 7h 30mOptimal
11:16 PM
6 cycles · 9h Optimal ✓
9:46 PM
Includes 14 minutes to fall asleep — the average for healthy adults. Waking between cycles leaves you feeling groggy; waking at the end of a cycle is when you're in lightest sleep.
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