Sleep Calculator
Get bedtimes or wake-up times aligned to 90-minute sleep cycles so you wake refreshed.
How to use it
- Choose a mode Set a wake time, or start from now.
- Enter the time When you want to wake, or your bedtime.
- Pick a row Each option completes whole sleep cycles.
Examples
| wake 07:00 | bed 21:45 (6 cycles) |
|---|---|
| bed 23:00 | wake 06:45 (5 cycles) |
About this tool
Waking up mid-cycle is what leaves you groggy, even after a long night. This calculator works backwards or forwards through 90-minute sleep cycles to suggest bedtimes or wake-up times that let you wake between cycles.
Tell it when you need to be up and it lists bedtimes for five, six or more complete cycles; or start from now and it suggests when to set the alarm. It even allows time to fall asleep. Sleep needs vary, so treat it as a helpful guide. It runs in your browser.
Frequently asked questions
Why 90-minute cycles?
Sleep moves through cycles of roughly 90 minutes. Waking at the end of a cycle, rather than the middle, tends to leave you feeling more refreshed.
Does it account for falling asleep?
Yes. It adds about 15 minutes to fall asleep, so the suggested times line up with actual sleep rather than lights-out.
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Updated June 14, 2026