Sleep Calculator
Wake up refreshed with 90-minute sleep cycles
If you go to bed now (--:--), these are the best times to wake up
* Includes the average 15 minutes it takes to fall asleep.
When should you wake up if you sleep now
Sleep moves through roughly 90-minute cycles of light and deep sleep, and waking mid-cycle leaves you groggy no matter how long you slept. This calculator finds the best wake-up times if you go to bed now, or works backwards from your alarm to the ideal bedtime — including the average 15 minutes it takes to fall asleep. Everything runs in your browser.
Times are aligned to 90-minute sleep cycles so you wake in light sleep.
Works both ways: wake-up times if you sleep now, or bedtimes for your alarm.
Adds the ~15 minutes most people need to actually fall asleep.
Frequently asked questions
Sleep alternates between light, deep and REM stages in roughly 90-minute cycles. Waking at the end of a cycle, during light sleep, leaves you far more refreshed.
Adults are recommended 5–6 cycles (7.5–9 hours). Four cycles (6 hours) is a minimum, and three (4.5 hours) should be an emergency only.
Ninety minutes is an average; real cycles range from 80 to 110 minutes. Adjust your wake time over a few days to find what fits you.