Sleep Cycle Calculator
Bedtimes that let you wake between cycles, not mid-cycle.
Enter your values
Results update instantly as you type — no submit needed.
Results
- Best bedtime (6 cycles, 9 h)
- 21:15
- Good bedtime (5 cycles, 7.5 h)
- 22:45
- Minimum (4 cycles, 6 h)
- 00:15
| Cycles | Sleep length | Go to bed at |
|---|---|---|
| 6 | 9 h | 21:15 |
| 5 | 7.5 h | 22:45 |
| 4 | 6 h | 00:15 |
| 3 | 4.5 h | 01:45 |
Quick answer
Sleep runs in roughly 90-minute cycles, so waking at the end of a cycle — after 5 or 6 cycles — feels far better than waking mid-cycle.
Sleep time = 90 min × cycles + 15 min to fall asleep
How to use the Sleep Cycle Calculator
- 1Enter your wake time as a decimal hour, e.g. 6.5 for 06:30.
- 2Adjust how long you take to fall asleep.
- 3Pick a bedtime from the table.
Frequently asked questions
Is every cycle exactly 90 minutes?
No — cycles range from 70 to 120 minutes and lengthen through the night, so treat these as close approximations.
Is 6 hours enough?
For most adults no. The evidence supports 7–9 hours; 6 is a fallback, not a target.