Sleep Cycle Calculator

Wake up feeling refreshed by aligning your alarm with the end of a sleep cycle. Each cycle lasts roughly 90 minutes and includes light sleep, deep sleep, and REM stages. Waking mid-cycle — especially during deep sleep — causes grogginess even if you slept enough hours. This calculator tells you the best times to wake up (or fall asleep) based on 90-minute cycles.

Enter the time you plan to go to bed and the calculator shows optimal wake-up times, or enter when you need to wake up and it shows the best bedtimes. It factors in an average 14-minute sleep onset latency so the math accounts for the time it takes to actually fall asleep.