Sleep Calculator

Plan bedtimes and wake-ups around sleep cycles — locally, in your browser.

No signup · No uploads · Calculations stay on your device

Plan around

Enter the time your alarm goes off.

Typical adult average: 15 min.

Commonly used average: 90 min.

Suggested bedtimes for a 07:00 wake-up

  1. 21:45tonight6 sleep cycles · 9 h 15 min in bed
  2. 23:15tonight5 sleep cycles · 7 h 45 min in bed Closest to 8 h
  3. 00:45today4 sleep cycles · 6 h 15 min in bed
  4. 02:15today3 sleep cycles · 4 h 45 min in bed

Results are planning estimates built from average sleep-cycle lengths and a configurable time-to-fall-asleep. They are not medical advice, not a sleep diagnosis, and not a guarantee that you will fall asleep or wake up on cue.

How the sleep calculator works

Sleep typically arrives in repeating cycles of roughly 90 minutes (light sleep, deep sleep, REM), and most adults take about 15 minutes to fall asleep after lights out. This tool works those two averages into simple planning arithmetic: pick the time you want to wake up and it suggests bedtimes for 3–6 full cycles, or pick a bedtime (or "sleep now") and it suggests wake-up times. You can adjust both assumptions — time to fall asleep and cycle length — in the form, and the estimates update instantly.

The results are planning estimates, not medical advice. They do not measure your sleep architecture, cannot diagnose a sleep problem, and do not guarantee you will fall asleep or wake at the suggested minute. If you regularly struggle to sleep well, talk to a qualified health professional. Every calculation happens on your device: there is no account and no server request for the calculation. The browser may remember your selected mode, times, onset estimate and cycle length in local storage so the calculator reopens with your preferences; those settings stay on your device and can be cleared with this site's browser data. Read the Privacy Policy.