Sleep Cycle Calculator

Best bedtimes & wake-up times

Go to bed at one of these times

09:45 PM

6 cycles · 9 h sleep · recommended

11:15 PM

5 cycles · 7.5 h sleep · recommended

12:45 AM

4 cycles · 6 h sleep

02:15 AM

3 cycles · 4.5 h sleep

Sleep runs in ~90-minute cycles; waking mid-cycle causes grogginess. Times include ~15 minutes to fall asleep. Adults generally need 5–6 cycles (7.5–9 hours).

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About the Sleep Cycle Calculator

Find the best bedtime or wake-up time based on 90-minute sleep cycles: enter when you wake up (or go to bed) and get four scientifically sensible options, accounting for ~15 minutes to fall asleep. Wake between cycles, not in the middle of one, and feel less groggy.

How to use

1Choose “I wake up at…” or “I go to bed at…”.
2Set the time.
3Pick one of the recommended cycle-aligned times.

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Sleep Cycle Calculator is part of DevKit — 100 free, privacy-first tools for developers, students, and everyone, built by Minhazul Ashim. Everything runs in your browser; your data never leaves your machine.