Free Sleep Cycle Calculator Online
Calculate optimal wake-up times based on bedtime, or optimal bedtime based on wake-up time, using 90-minute sleep cycle science to wake during light sleep. — 100% free online utility, zero sign-up, zero paywalls, and private client-side processing.
How It Works
Choose Calculation Direction
Select 'I want to wake at X, when should I sleep?' or 'I'm sleeping at X, when should I wake?'
Enter Time
Input your desired wake-up or sleep time.
View Optimal Times
See 4–6 optimal sleep or wake times based on 90-minute REM cycle boundaries.
Frequently Asked Questions
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