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Sleep Calculator
Best wake-up times · Sleep cycles · REM sleep
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❓ Frequently Asked Questions
How many hours of sleep is ideal? ▾
Adults need 7-9 hours (5-6 complete sleep cycles). Each cycle is 90 minutes. Waking up mid-cycle causes grogginess. This calculator finds times that align with complete cycles.
What is a sleep cycle? ▾
A sleep cycle lasts ~90 minutes and includes light sleep, deep sleep, and REM (dream) sleep. Completing full cycles = waking up refreshed.
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