Is a sleep cycle always 90 minutes?

No. Ninety minutes is a convenient average. Real NREM and REM cycles vary by person and by night, so the calculator gives planning windows rather than exact stage timing.

Should I choose five or six cycles?

For many adults, five cycles gives about 7.5 hours asleep and six cycles gives about 9 hours asleep. Choose the option that fits your schedule and the age-based range.

Can this help with insomnia or sleep apnea?

No. It is not medical advice and does not diagnose or treat sleep disorders. Recurrent insomnia, loud snoring, breathing pauses or severe daytime sleepiness should be discussed with a clinician.

Sleep Calculator

Calculate bedtime or wake-up time options from 90-minute sleep cycles, fall-asleep time and age-based sleep-duration ranges.

Mode

Wake up at

Age

Fall asleep, minutes

This sleep calculator uses 90-minute sleep cycles as a planning estimate. It is not medical advice and does not diagnose insomnia, sleep apnea or other sleep disorders.

Bedtime options

Adult (18-64) | recommended 7 h-9 h

Results assume 90-minute sleep cycles and 14 minutes to fall asleep. The options are planning windows between cycles, not a guarantee that you will feel rested.

N1 light sleepN2 light sleepN3 deep sleepREMwake-up window

Sleep cycle calculator for bedtime and wake-up times

English search intent for a sleep calculator is usually action-first: choose when you need to wake up, or choose when you are going to bed, and get several practical timing options.

t_{bed} = t_{wake} - n \cdot 90 - L

Use this direction when you know the wake-up time. L is the estimated minutes to fall asleep.

t_{wake} = t_{bed} + L + n \cdot 90

Use this direction when you know the bedtime. n is the number of full 90-minute sleep cycles.

Planning estimate, not medical advice

This calculator does not diagnose sleep disorders and cannot measure your actual sleep stages. Talk with a clinician if insomnia, loud snoring, pauses in breathing or severe daytime sleepiness keep recurring.

How to use the results

Five or six cycles usually align better with adult overnight sleep than three or four cycles.
Change the fall-asleep time if you usually take more or less than the default estimate.
Use the age range as a broad reference for sleep duration, not as a diagnosis of sleep quality.
The hypnogram is a simplified N1, N2, N3 and REM preview, not a personal sleep study.

Sleep duration ranges

Age	General sleep range	How to read it
1-2 years	11-14 hours	Usually includes naps.
3-5 years	10-13 hours	Usually includes naps.
6-12 years	9-12 hours	School-age children generally need longer sleep.
13-17 years	8-10 hours	Sleep debt can build quickly.
18-64 years	7-9 hours	Common adult reference range.
65+ years	7-8 hours	Sleep pattern and timing may change.

Frequently Asked Questions

Sources and References

Calculations are based on the listed reference sources. Links open in a new tab.

Updated: June 2, 2026

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