Sleep cycle calculator
Tell it when the alarm goes off and get the bedtimes that land between 90-minute sleep cycles — or start from bedtime and see when to wake. Free, instant, no sign-up.
Includes 15 minutes to fall asleep. Cycles average 90 minutes but vary from person to person.
Hit the bedtime — then actually switch off
Reset gives the last few minutes of the day one small ritual: five minutes of breathwork, a line of journaling, a soundscape or a gentle stretch, already picked when you open it. A dusk interface that's readable in bed, and a streak that counts good nights instead of punishing missed ones.
Sleep cycles, answered
How does a sleep cycle calculator work?
Sleep runs in cycles of roughly 90 minutes, each moving from light sleep through deep sleep to REM. Waking at the end of a cycle, when sleep is lightest, tends to feel easier than being pulled out of deep sleep. The calculator counts back (or forward) in 90-minute steps from the time you give it and adds the minutes it takes you to fall asleep.
How many sleep cycles do I need?
Most adults need 7 to 9 hours of sleep a night, which is about five or six full cycles. Five cycles is 7½ hours of sleep; six is 9. Fewer than four cycles (6 hours) regularly leaves most people short. Treat four as a rough-night fallback, not a plan.
Are sleep cycles always exactly 90 minutes?
No — 90 minutes is an average. Cycles vary from about 70 to 120 minutes between people and even across one night, with more deep sleep early and more REM toward morning. Use the times as a starting point: if you keep waking groggy, nudge the fall-asleep time by 10–15 minutes and see whether mornings get easier.
Why does it add 15 minutes to fall asleep?
Most people take somewhere between 10 and 20 minutes to drift off, so 15 is the default. If you are usually out the moment your head hits the pillow, set it lower; if you lie awake for a while, set it higher. Falling asleep in under five minutes every night can be a sign you are short on sleep.