Sleep Cycle Calculator
Work backwards from your wake-up time to find the bedtimes that let you finish a full sleep cycle, rather than waking mid-cycle.
How to use the Sleep Cycle Calculator
- Enter the time you need to wake up, or the time you plan to sleep.
- Read the suggested times that complete full cycles.
- Pick the option that gives you five or six cycles.
About the Sleep Cycle Calculator
Sleep runs in cycles of roughly ninety minutes, and waking at the end of one feels dramatically better than waking in the middle of deep sleep — which is why seven and a half hours can leave you sharper than eight. The calculator adds about fifteen minutes for falling asleep. Cycle length varies between people, so treat the suggested times as a starting point and adjust based on how you actually feel.
Please note: this is a general wellness estimator, not a medical assessment. It does not diagnose, treat or prevent any condition, and measures like BMI are known to misclassify athletes, older adults and pregnant women. Speak to a qualified clinician about any health concern. Full disclaimer.
Frequently asked questions
How long is a sleep cycle?
About 90 minutes on average, though it varies between individuals and across the night.
How many hours of sleep do I need?
Most adults need seven to nine hours — five to six complete cycles.
Why do I feel worse after more sleep?
Waking in the middle of deep sleep leaves you groggy. Ending on a cycle boundary usually feels better even if the total is slightly shorter.
Should I set my alarm at a cycle boundary?
It helps. A sleep cycle runs about 90 minutes, and waking at the end of one feels easier than being pulled out of deep sleep mid-cycle. The tool suggests alarm times that land on those boundaries, allowing about fifteen minutes to fall asleep.
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