Sleep Calculator
GoCalc
Calculate the best time to go to sleep or wake up based on 90-minute sleep cycles. Wake up feeling refreshed by completing full cycles.Updated 2026-03-16
Sleep Cycles Explained
| Cycles | Sleep Duration | Quality |
|---|---|---|
| 3 cycles | 4.5 hours | ⚠️ Minimum (not recommended) |
| 4 cycles | 6 hours | ⭐⭐ Adequate for short term |
| 5 cycles | 7.5 hours | ⭐⭐⭐ Recommended for most adults |
| 6 cycles | 9 hours | ⭐⭐⭐ Ideal / Recovery sleep |
* Each cycle is ~90 minutes. 15 minutes is added for the average time it takes to fall asleep.
How the Sleep Calculator Works
Sleep happens in cycles of approximately 90 minutes each. Waking up between cycles (rather than in the middle of one) helps you feel more refreshed and alert.
This calculator counts back in 90-minute intervals from your desired wake time, adding 15 minutes for the average time to fall asleep.
For example, if you need to wake at 7:00 AM: 6 cycles = 9h + 15min = bedtime at 9:45 PM.
💡 Most adults need 5-6 sleep cycles (7.5-9 hours) per night. All calculations happen locally in your browser.
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