Health & Fitness Calculators
Sleep Cycle Calculator
Enter a wake time or bedtime to calculate recommended times based on completing full 90-minute sleep cycles.
Recommended bedtimes:
9:45 PM
6 cycles (9.0h sleep)
11:15 PM
5 cycles (7.5h sleep)
12:45 AM
4 cycles (6.0h sleep)
2:15 AM
3 cycles (4.5h sleep)
3:45 AM
2 cycles (3.0h sleep)
5:15 AM
1 cycles (1.5h sleep)
Based on ~90-minute sleep cycles plus 15 minutes to fall asleep — waking up between cycles (rather than mid-cycle) tends to feel less groggy.
How to use this tool
- 1Choose wake time or bedtime mode.
- 2Enter the time.
- 3See recommended times for 4-6 full sleep cycles.
Frequently asked questions
Why do sleep cycles matter?+
Waking up between cycles (rather than mid-cycle, during deep sleep) tends to feel less groggy, even at the same total sleep duration.