I want to, Time (24-hour), Minutes to fall asleep
Sleep Cycle Calculator
Find bedtimes or wake-up times that line up with complete sleep cycles.
Waiting for input
How this calculator works
Sleep moves through light, deep and REM stages in cycles that average about 90 minutes. Waking at the end of a cycle usually feels easier than waking from deep sleep. The calculator counts back or forward in 90-minute steps and adds the time you need to fall asleep. Most adults need five or six cycles, which is 7.5 to 9 hours.
Formula
- Bedtime = wake time − (cycles × 90 min) − time to fall asleep
- Wake time = bedtime + time to fall asleep + (cycles × 90 min)
Worked example
Waking at 7:00 AM
- I want to
- Wake up at this time
- Time (24-hour)
- 07:00
- Minutes to fall asleep
- 15
ResultGo to bed at 11:15 PM or 9:45 PM
Five or six full cycles for a 7:00 AM wake-up, allowing 15 minutes to fall asleep.
Things to keep in mind
- Cycle length varies from about 70 to 120 minutes between people and through the night, so treat the times as a guide.
- For general information only. It is not medical advice; talk to a health professional about your own situation.
Frequently asked questions
How long is one sleep cycle?
About 90 minutes on average for adults, with a normal range of roughly 70 to 120 minutes. Early cycles contain more deep sleep and later ones more REM sleep.
How many hours of sleep do adults need?
The CDC recommends at least 7 hours a night for adults aged 18 to 60. That is five cycles (7.5 hours) for most people.
How long does it take to fall asleep?
Around 10 to 20 minutes is typical. The calculator uses 15 minutes by default; change it if you know you take longer.
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Results are estimates based on the values you enter and the published method shown above. They do not replace professional medical, financial or legal advice. Method reviewed October 7, 2026. About this site