Sleep calculator
The times stay in this tab. Nothing is uploaded.
Go to bed at
One sleep cycle is about 90 minutes and falling asleep takes about 14 minutes.
Cycle lengths differ from person to person; a general guide, not medical advice.
How to use this tool
Find a bedtime that ends on a full sleep cycle, or the best times to wake up. Nothing is uploaded.
Open Sleep calculator
Wake-up time is selected and 07:00 is filled. Four bedtimes for 6 to 3 cycles sit on the right.
Set your wake-up time
Change the time to your alarm. Five or six cycles are the usual target; the shorter options are for short nights.
Or start from bedtime
Switch to Bedtime and enter when you lie down to see wake-up times. Copy puts the list on the clipboard.
FAQ
How does the sleep calculator work?
Sleep runs in cycles of about 90 minutes. The tool counts back from your wake-up time (or forward from your bedtime) in whole cycles and adds about 14 minutes to fall asleep, so an alarm lands at the end of a cycle instead of in deep sleep.
Is anything uploaded?
No. The times are computed in this tab and nothing is sent or stored.
How many cycles should I sleep?
Five or six cycles (7.5 to 9 hours) suit most adults. Three or four cycles are shown for short nights; use them when you must, not every night.
Why does it add 14 minutes?
Most people take 10 to 20 minutes to fall asleep. The calculator uses 14 minutes as an average; if you drop off faster or slower, shift the result by the difference.
Is a 90-minute cycle exact?
No. Cycles range from about 70 to 120 minutes and change through the night, so treat the times as a starting point and adjust by how you feel on waking.