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Sleep Time Calculator - When to Sleep & Wake
Free sleep time calculator. Calculate the best time to sleep or wake up based on sleep cycles. Wake up refreshed, not groggy.
Sleep Time Calculator
Calculate optimal sleep and wake times
Suggested Times
Enter your values to see results
and click the "Calculate" button
Sleep Time Calculator
Calculate when to sleep or wake based on 90-minute sleep cycles. Waking between cycles helps you feel more refreshed.
Sleep Cycles
Each cycle ≈ 90 minutes. Add 15 min to fall asleep.
Complete cycles (not hours) determine sleep quality. 5 cycles (7.5 hours) is ideal for most adults.
Frequently Asked Questions
Why 90-minute cycles?
Sleep has stages (light, deep, REM). One full cycle through all stages takes about 90 minutes. Waking mid-cycle causes grogginess.
How much sleep do I need?
Adults: 7-9 hours (5-6 cycles). Teens: 8-10 hours. Children: 9-12 hours. Quality matters as much as quantity.
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