Sleep Calculator
Suggested bedtime based on your wake-up time and 90-minute sleep cycles.
Worth Knowing
This tool counts backward from your wake time in 90-minute blocks because a full sleep cycle — light, deep, and REM stages — runs roughly that long, and waking at the end of a cycle rather than mid-deep-sleep tends to leave you feeling less groggy. The 90-minute figure is an average, though; real cycles range from about 70 to 120 minutes and lengthen through the night, so use the suggested times as a nudge toward consistent sleep timing rather than a precise alarm science.
How to Use
- Enter Wake-up time into the Sleep Calculator above.
- Your result appears instantly as you type — there's no submit button or page reload.