Sleep cycle calculator
Calculate the best times to wake up or go to sleep based on 90-minute sleep cycles. Avoids waking mid-cycle for fresher mornings.
- Free, no sign-up
- No data stored
- Reviewed 2026-01-15
Your details
Results
- Recommended sleep
- 7–9 h
- Cycle length
- 90 min
- Fall asleep time
- 15 min
For age 30
Bedtimes table
| Time | Cycles | Sleep duration | Recommended |
|---|---|---|---|
| 21:45 | 6 | 9:00:00 | ✓ |
| 23:15 | 5 | 7:30:00 | ✓ |
| 00:45 | 4 | 6:00:00 | |
| 02:15 | 3 | 4:30:00 |
Sleep table note
Sleep note
About the Sleep Calculator
Sleep cycles last approximately 90 minutes. Waking at the end of a cycle (rather than mid-cycle) typically leaves you feeling more refreshed. Enter your bedtime or desired wake time and the calculator suggests optimal times based on 4–6 full cycles plus time to fall asleep.
How to use the Sleep Calculator
- Choose mode: "I want to wake at…" or "I plan to sleep at…".
- Enter the time.
- Adjust fall-asleep time (default 15 min).
- Optionally adjust cycle length.
- View suggested times.
Frequently asked questions
Why 90 minutes per cycle?
90 minutes is the average adult sleep cycle length, progressing through light sleep, deep sleep and REM. Individual cycles range from 80–120 minutes.
How many cycles do I need?
Most adults need 5–6 cycles (7.5–9 hours). Fewer than 4 cycles (6 hours) is generally insufficient for long-term health.
Does age affect sleep cycles?
Yes. Older adults tend to have shorter cycles and less deep sleep. The calculator lets you adjust cycle length by age group.