๐ดSleep Cycle / Wake Time
Find optimal wake or bed times based on 90-minute sleep cycles. Useful for deciding nap length after a late shift, optimal bedtime before a morning exam or interview, and jet lag planning.
How to use
- 1Enter your target wake or bedtime.
- 2Recommended times appear.
FAQ
Why 90-minute cycles?+
One sleep cycle (REM-NREM) averages 90 minutes. Waking mid-cycle feels tired; waking at cycle end feels refreshed.
Don't cycles vary by person?+
Individual cycles range 80~110 minutes. 90 is an average; could be off by ยฑ15 minutes.
How many hours should I sleep?+
Adults need 7~9 hours (4~6 cycles). 4 cycles (6h) is minimum; 5 cycles (7.5h) is recommended.
How long to fall asleep?+
Usually 10~20 minutes assumed. The tool adds this automatically.
Naps in 90-min units too?+
Naps are best at 20~30 min (light recovery) or 90 min (one full cycle). 60-min naps wake you mid-deep-sleep, often leaving you groggier.
Isn't sleep quality more important?+
Yes. Beyond duration, dark environment, consistent timing, and reducing caffeine also matter for sleep hygiene.