Sleep Cycle Calculator
Enter the time you want to wake up.
Best bedtime
23:15
5 cycles (7.5h)
21:45
6 cycles · 9h
23:15
5 cycles · 7.5h
00:45
4 cycles · 6h
02:15
3 cycles · 4.5h
Assumes 15 min to fall asleep + 90-min cycles.
How it works
Each sleep cycle is 90 min. Waking between cycles (not mid-cycle) reduces grogginess. We compute bedtimes that end on a full cycle.
Formula
Bedtime = wake time − (cycles × 90) − 15 min (to fall asleep)
Worked example
Wake 07:00 → best bedtime 22:00 (6 cycles) or 23:30 (5 cycles).
FAQ
- How many cycles?
- 5–6 cycles (7.5–9 hours) for most adults.
- Always 90 min?
- Average only — actually 70–110 minutes.
- Naps?
- 20–30 min or a full 90-min cycle work best.