Sleep Cycle Calculator
Suggests optimal wake-up or bedtimes based on 90-minute sleep cycles for refreshing mornings.
Input
Recommended Bedtimes
21:45
6cycles（9hours）23:15Recommended
5cycles（7.5hours）00:45
4cycles（6hours）02:15
3cycles（4.5hours）How to Use
Select the calculation mode and enter a wake-up time or bedtime to see optimal times based on sleep cycles. Five cycles (7.5 hours) is the recommended sleep duration for most people.
How It Works
Human sleep repeats approximately 90-minute cycles of REM and non-REM sleep. Waking at the end of a cycle makes it easier to feel refreshed. This tool assumes an average of 15 minutes to fall asleep and calculates 3 to 6 cycle options (4.5 to 9 hours). Individual variation exists, so use this as a guide.