Sleep Cycle Calculator
Suggest wake-up or bedtime options aligned to 90-minute sleep cycles so you wake refreshed, accounting for time to fall asleep. Everything runs in your browser.
Enter a time as HH:MM
FAQ
Why 90-minute cycles?
Sleep repeats light→deep→REM stages in ~90-minute cycles. Waking mid-deep-sleep feels awful; waking between cycles feels easier. Individual cycles range 80–110 minutes.
How many cycles should I sleep?
Adults generally do best with 5 cycles (7.5 hours); 4 cycles (6 hours) is a reasonable floor. The tool highlights the 5-cycle option.
Why 15 minutes to fall asleep?
Healthy adults typically take 10–20 minutes to fall asleep—adjust to your own pattern.
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