Sleep Cycle Bedtime Calculator
Enter the time you need to wake up to see ideal bedtimes.
Result
How to use
- Enter your values in the fields above.
- Press Calculate to see your result instantly.
- Use the Share button to copy a link to your result.
About this calculator
A full night's sleep is made of repeating ~90-minute sleep cycles, each moving through light sleep, deep sleep, and REM. Waking up in the middle of a cycle — especially during deep sleep — tends to leave people feeling groggy (sleep inertia), while waking between cycles tends to feel more refreshing, even at the same total sleep duration.
This calculator works backward from your target wake-up time in 90-minute blocks, and adds roughly 15 minutes for the average time it takes to actually fall asleep, to suggest bedtimes aligned with complete cycles — the same logic behind popular sleep-cycle calculators used by people optimizing their sleep schedule around alarms, shift work, or travel.
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