Sleep Cycle Calculator
Enter a wake-up time to see suggested bedtimes, or a bedtime to see suggested wake-up times.
| Sleep cycles | Time asleep | Go to bed at |
|---|---|---|
| 6 | 9h | 9:45 PM |
| 5 | 7.5h | 11:15 PM |
| 4 | 6h | 12:45 AM |
| 3 | 4.5h | 2:15 AM |
| 2 | 3h | 3:45 AM |
| 1 | 1.5h | 5:15 AM |
Based on roughly 90-minute sleep cycles plus about 15 minutes to fall asleep. Actual cycle length varies by person; this is a planning heuristic, not medical advice.
About this tool
Waking up in the middle of a deep sleep stage can leave you groggy, even after a full night. The Sleep Cycle Calculator helps you plan around that by suggesting bedtimes and wake-up times aligned to roughly 90-minute cycles. Enter the time you want to wake up and see good times to fall asleep, or enter when you are going to bed and see times to set your alarm. It also makes it easy to compare a five-cycle night with a six-cycle night, and to build in the time most people need to drift off. The tool is a planning guide only. It is not a medical device and does not offer medical advice, and individual sleep needs vary. Everything runs locally in your browser, so nothing about your schedule leaves your device. Napping instead? Use the Online Timer for a short power nap, and wind down beforehand with Box Breathing. If you need to measure the gap between two times exactly, the Time Duration Calculator does the arithmetic. See more daily-routine helpers in the Wellness tools, and check the World Clock when planning around a time zone change.
How does the sleep cycle calculator work?
How does the sleep cycle calculator work? It models sleep as roughly 90-minute cycles plus about 15 minutes to fall asleep, and suggests times that land at the end of a whole cycle rather than in the middle of one, which is commonly associated with feeling less groggy on waking.
Frequently asked questions
Is 90 minutes exact for everyone?
No, cycle length varies from about 70 to 120 minutes depending on the person and the night. This is a planning heuristic, not a measurement of your actual sleep.
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