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Bedtime calculator

Enter when you need to wake up, or when you are going to bed. Results update as you type.

Updated October 3, 2026 · 90-minute cycles + 15 min to fall asleep · NINDS, AASM, NSF

Counts in 90-minute cycles plus 15 minutes to fall asleep. How we calculate

How it works

bedtime = wake-up time − (cycles × 90 min) − 15 min. The calculator shows six, five and four cycles: 9 hours, 7 h 30 min and 6 hours of sleep. Five and six sit inside the 7–9 hours the National Sleep Foundation panel recommends for adults; four is a one-night floor. In the other direction, alarm = bedtime + 15 min + (cycles × 90 min).

Ninety minutes is an average. The AASM puts a cycle anywhere from 70 to 120 minutes, and the first cycle of the night is usually the shortest, so read each result as the middle of a window. Fifteen minutes is the typical time for a healthy adult to fall asleep; if you know yours is longer, move the bedtime earlier by the difference.

Prefer a page you can bookmark?

Every wake-up time from midnight to 11:45 pm has its own page with the timeline and table: bedtime by wake-up time. Bedtimes from 6 pm to 4 am: alarm by bedtime.

Sources

  1. Brain Basics: Understanding Sleep — National Institute of Neurological Disorders and Stroke (NIH)
  2. How Sleep Works - Sleep Phases and Stages — National Heart, Lung, and Blood Institute (NIH)
  3. Sleep cycles - Sleep Education — American Academy of Sleep Medicine
  4. Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the AASM and Sleep Research Society — Sleep 38(6):843-844, 2015

General information from population studies (NIH, CDC, NSF, AASM). It is not medical advice and does not replace a clinician who knows you.