Sleep Cycle Calculator On-device
Suggested bedtimes or wake-up times based on sleep cycles — runs entirely on your device.
Suggested bedtimes
Times include a 15-minute buffer to fall asleep.
The 90-minute cycle is a population average. Measured individual averages range from 63.5 to 119 minutes (SD ≈ 12 min), and cycle length shifts across the night — this tool cannot know your actual cycle boundaries.
Estimates based on average sleep cycles — not medical advice. If you have ongoing sleep problems, consult a clinician.
Free sleep cycle calculator: suggested bedtimes or wake-up times based on 90-minute sleep cycles, with honest notes on individual variation. Works entirely on your device.
About this tool
What you provide
- A wake-up time, or a bedtime.
- Which direction to work in: backward from a wake-up time, or forward from a bedtime.
What you get
- Three suggested times, one each for 4, 5 and 6 sleep cycles.
- The total sleep length for each suggestion.
Limits
- The 90-minute cycle is a population average; measured individual averages range from 63.5 to 119 minutes, so the tool cannot know your actual cycle boundaries.
- Estimates only, not medical advice; consult a clinician about ongoing sleep problems.
- Suggestions cover 4, 5 and 6 cycles only, and add a fixed 15-minute buffer to fall asleep.
How to use it
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Pick your direction
Choose "I want to wake at…" to work backward to a bedtime, or "I'm going to bed at…" to work forward to a wake-up time.
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Enter the time
Set the wake-up time or bedtime in the time field, and the suggestions update as soon as you change it.
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Read the suggested times
Three times are listed, one each for 4, 5 and 6 cycles, with the sleep length beside each and the fall-asleep buffer already added.
Frequently asked questions
How does the sleep cycle calculator work?
Enter a wake-up time or bedtime and it suggests times based on typical sleep cycles, calculated entirely on your device.
Is this medical advice about how much sleep I need?
No, it's a scheduling suggestion based on average sleep-cycle length, not medical guidance; consult a clinician for sleep concerns.
Is the tool free and private?
Yes, it's free and runs entirely on your device with nothing uploaded.