This sleep cycle calculator lays out suggested sleep and wake times using cycle lengths, falling-asleep time, and the chosen schedule.
Health
Sleep Cycle Calculator
Plan suggested sleep and wake times from sleep-cycle lengths.
Calculator
About this calculator
Formula notes
Suggested times are built by adding or subtracting the selected sleep-cycle durations from the sleep or wake reference time.
Worked examples
- Example: five 90-minute cycles plus 15 minutes to fall asleep totals 7 hours 45 minutes.
- Five 90-minute cycles plus 15 minutes to fall asleep represents 7 hours 45 minutes of scheduled sleep.
How to use it
- Choose whether you are starting from bedtime or wake-up time.
- Set the first and later cycle lengths if you need custom values.
- Compare the suggested times rather than treating one time as mandatory.
Frequently asked questions
Are all sleep cycles exactly 90 minutes?
No. Ninety minutes is a common planning approximation; real sleep cycles vary by person and across the night.
Does this diagnose sleep problems?
No. It only performs schedule arithmetic. Persistent sleep concerns should be discussed with a qualified clinician.
Limits and interpretation
- Sleep-cycle lengths vary across people and nights, so the schedule should be treated as a planning aid rather than a physiological measurement.
- The calculator cannot account for insomnia, awakenings, sleep disorders, medication effects, or the quality of the sleep itself.