Sleep Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles.
Recommended bedtimes (most recent cycle first)
09:45 PM
11:15 PM
12:45 AM
Comment ça marche
Counts back (or forward) in ~90-minute sleep cycles from your target wake-up time (or bedtime), plus about 15 minutes to fall asleep.
Why 90-minute cycles?
A full sleep cycle — light sleep, deep sleep, and REM — averages about 90 minutes; waking up between cycles rather than mid-cycle tends to feel less groggy.