Bedtime calculator by sleep cycles
Enter the time you want to wake up and the tool suggests bedtimes that fit 3 to 6 full sleep cycles.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter wake-up time, time to fall asleep and sleep cycle length.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Bedtime = wake time - (cycles × cycle length + minutes to fall asleep). Defaults: 90-minute cycles and 15 minutes to fall asleep.
Example
Inputs: Wake-up time = 06:30, Time to fall asleep = 15 min, Sleep cycle length = 90 min. Result: Go to bed at (5 cycles): 22:45; Go to bed at (6 cycles): 21:15; Go to bed at (4 cycles): 00:15.
Limits and caveats
- 90 minutes is a rough average; real cycles vary from person to person and night to night.
- It helps with timing only and is not a diagnosis of any sleep problem.
Questions about this tool
When should I sleep to wake at 6:30?
With 90-minute cycles and 15 minutes to fall asleep: 22:45 for five cycles or 21:15 for six.
Why do I sometimes wake up tired after a long sleep?
Waking in the middle of deep sleep can leave you groggy, so the tool aims for the end of a cycle.
Can I change the cycle length?
Yes, enter anything from 60 to 120 minutes if you find your cycle is shorter or longer.