Sleep cycle calculator
Set the time you want to wake and how long you usually take to fall asleep. The page lists bedtimes for 6, 5, 4 and 3 cycles.
- 90-minute cycles
- Free, no sign-up
Free to use, no account. More everyday tools
How to use it
- Set the wake time.
- Set minutes to fall asleep. 15 is the default.
- Read the bedtimes. Six cycles is the longest sleep on the list.
How a bedtime is chosen
Each cycle is 90 minutes. The page subtracts the cycles plus the time to fall asleep from the wake time. Six cycles and 15 minutes is 9 hours 15 minutes earlier. The idea is to wake at the end of a cycle rather than in the middle of one. Real sleep is not a perfect 90-minute clock.
This does not treat insomnia, shift work or a medical sleep problem. It is a bedtime subtraction.
Private by design
Privacy
The time stays in this tab and is not uploaded.
Questions
Why 90 minutes?
It is the usual length quoted for a sleep cycle. Your own cycles can differ.
Which row should I pick?
Six cycles is about nine hours in bed. Pick the one that matches how long you can actually sleep.
Does it set an alarm?
No. It only shows times.