How to Time Sleep by 90-Minute Cycles
Sleep runs in cycles of about 90 minutes, and it typically takes about 15 minutes to fall asleep. Going to bed at 23:00 puts you asleep by 23:15, so 5 full cycles end around 06:45 and 6 cycles around 08:15.
Open the interactive Everyday Lifestyle tool →Formula: wake time = bedtime + 15 min + (cycles x 90 min)
Key facts
| Formula | wake time = bedtime + 15 min + (cycles x 90 min) |
|---|---|
| Cycle length | ~90 minutes |
| Time to fall asleep | ~15 minutes |
| Bedtime 23:00, 5 cycles | wake ~06:45 |
| Bedtime 23:00, 6 cycles | wake ~08:15 |
Frequently asked questions
What time should I go to bed to wake at 07:00?
For 5 cycles, about 23:15; for 6 cycles, about 21:45 (working backward: wake time minus cycles x 90 min minus 15 min to fall asleep).
Why 90-minute cycles?
A full sleep cycle (light, deep, and REM sleep) typically lasts about 90 minutes; waking near the end of a cycle rather than mid-cycle tends to feel less groggy.
Is the 15-minute fall-asleep time fixed?
No, it varies by person. It is used here as a typical estimate; adjust it based on your own experience.
Related pages
The calculations on this page are estimates based on common general-purpose formulas. They are not medical advice -- consult a doctor or other qualified professional for decisions about your health.
Sleep Cycle Calculator is part of Everyday Lifestyle on GOAT Lab — a free reference you can use without signing up, and it works offline. Open the tool above for any custom value.
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