Bedtime & Sleep Cycle Calculator
Work back from your alarm in 90-minute sleep cycles.
Sleep runs in ~90-minute cycles; waking between cycles feels far better than mid-cycle. Times include your “fall asleep” lag — go lie down at one of these and aim for 5–6 cycles (7.5–9 h).
How to use the Bedtime & Sleep Cycle tool
- Enter your sleep calculator in the fields above.
- Adjust any slider or type an exact number — the answer updates as you go.
- Copy the result and close the tab. Nothing you entered was sent anywhere.
About the Bedtime & Sleep Cycle tool
Pick your wake-up time and how long falling asleep takes you; the calculator lists bedtimes at whole sleep cycles of 7.5 and 9 hours, plus shorter options.
Waking mid-cycle groggy but at the top of a cycle refreshed is well documented — the 90-minute rhythm is the reason 6 hours can feel better than 7 hours 10 minutes.
Everything runs locally in your browser: no data is uploaded, no account is needed, and it works offline once the page has loaded.
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