Sleep Cycle Calculator
Show approximate cycle-aligned candidate bed/wake times without implying that every sleep cycle lasts exactly 90 minutes.
Enter or adjust the values above, then calculate.
Sleep Cycle: approximate Bed & Wake Times
Show approximate cycle-aligned candidate bed/wake times without implying that every sleep cycle lasts exactly 90 minutes.
Inputs this tool uses
- Calculate from
- Time
- Approximate cycle length
- Sleep-onset buffer
What you get
Approximate cycle-aligned planning times.
How to use the Sleep Cycle Calculator
- Enter calculate from, time, approximate cycle length and the other fields relevant to this calculation.
- Select any method, activity level or option shown on this page, then choose Calculate.
- Read the main result together with the supporting values, method, assumptions and limitations below before using the estimate.
How this calculation works
Sleep tools use date/time arithmetic. Any cycle-aligned suggestions are approximate and do not assume every sleep cycle is exactly 90 minutes.
Example calculation
The sample values loaded into the calculator produce 23:15. This example exists to show how the output is structured; replace the sample values with your own inputs for your calculation.
Assumptions and limitations
- Sleep needs and sleep-cycle length vary between people and nights.
- Use results for planning, not diagnosis of a sleep disorder.
Sources and review status
Source set last verified 2026-09-25. No clinician review is claimed unless a real named reviewer is displayed.
Questions people ask about Sleep Cycle Calculator
Should I wake only at the end of a 90-minute cycle?
No. Real sleep cycles are not fixed at exactly 90 minutes. The tool shows approximate planning candidates and lets you change the assumed cycle length.
Connected tools
Continue with the closest related calculation without re-entering sensitive values automatically.
Plan a sleep window from desired bedtime/wake time and duration, with optional approximate cycle visualization.
Open tool →☾Bedtime CalculatorCalculate a bedtime from desired wake time, sleep duration and optional sleep-onset buffer.
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Open tool →