Time & Date
Sleep Cycle Calculator
Calculate ideal bedtimes or wake times based on 90-minute sleep cycles.
Formulas and edge cases are reviewed against authoritative references before publication. For methodology, editorial standards, or corrections, use the links below.
Frequently asked questions
What is a sleep cycle?
A complete cycle through all sleep stages (light, deep, REM) lasting about 90 minutes.
Why wake between cycles?
Waking during deep sleep causes grogginess. Waking at cycle end leaves you refreshed.
How many cycles do I need?
Most adults need 4-6 cycles (6-9 hours). Quality matters as much as quantity.
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About this tool
This Sleep Cycle Calculator turns your inputs into practical results. Provide Time, Fall asleep time, and Wake-up time to calculate Duration and Recommendations.
Adjust values to compare scenarios and see how sensitive the result is. The calculation uses the numbers as entered, so double-check units and expect small differences from rounding in the displayed totals.