Sleep calculator
Pick a wake-up time to see when to go to bed, or a bedtime to see when to wake up, counted in whole sleep cycles of about 90 minutes.
Cycle length and time to fall asleep
The times count whole cycles after you fall asleep. Your own cycle and your own time to fall asleep may differ.
How it works
Sleep comes in cycles. The Sleep Foundation says a cycle lasts about 90 to 120 minutes, and its calculator allows 15 minutes to fall asleep and at least four full cycles. This calculator does the same arithmetic.
To find a bedtime, it takes your wake-up time and counts back whole cycles, and then the minutes it takes you to fall asleep. To find a wake-up time, it starts from your bedtime, adds the minutes to fall asleep, and then adds whole cycles. It shows four, five and six cycles.
A worked example
You want to wake at 7:00 am. Six cycles of 90 minutes is 9 hours, and 15 more minutes to fall asleep makes 9 hours and 15 minutes, so you go to bed at 9:45 pm. Five cycles is 7.5 hours, and the bedtime is 11:15 pm. Four cycles is 6 hours, and the bedtime is 12:45 am.
Going the other way, a bedtime of 11:00 pm gives wake-up times of 5:15 am for four cycles, 6:45 am for five and 8:15 am for six.
Make it fit you
A cycle and the time to fall asleep differ from person to person. You can set the cycle from 90 to 120 minutes and the time to fall asleep from 0 to 60. The calculator does not measure your sleep, and it cannot tell you how much sleep you need. If you often cannot sleep, talk to a doctor.
Sources
- Sleep Foundation sleep calculator, read on 2026-10-31.
Questions
What time should I go to bed if I wake up at 7?
With a 90 minute cycle and 15 minutes to fall asleep, 9:45 pm gives six cycles, 11:15 pm gives five and 12:45 am gives four.
How long is a sleep cycle?
The Sleep Foundation says a cycle lasts about 90 to 120 minutes. The calculator starts at 90 and lets you set any length from 90 to 120.
How many sleep cycles do I need?
The Sleep Foundation says to allow for at least four full cycles. The calculator shows four, five and six, which at 90 minutes is 6, 7.5 and 9 hours of sleep.
How long does it take to fall asleep?
The Sleep Foundation’s calculator allows about 15 minutes, and this one starts there. Set your own, from 0 to 60 minutes.
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