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Sleep Calculator

Pick the time you need to wake up, or the time you're going to bed, and get times that line up with whole sleep cycles.

Updated . An estimate for general education, not medical advice.

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Leave it at 15 if you're not sure.

Your result

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How the times are worked out

Through the night you move through non-REM and REM sleep several times. A clinical review puts it at about 4 to 6 cycles a night, averaging 90 minutes each. The calculator counts back from your wake time (or forward from your bedtime) in 90-minute steps, and adds the minutes you usually take to fall asleep.

Bedtime
wake time − (cycles × 90 min) − time to fall asleep
Wake time
bedtime + time to fall asleep + (cycles × 90 min)

Hours matter more than cycles

The American Academy of Sleep Medicine and the Sleep Research Society recommend that adults sleep 7 or more hours a night on a regular basis. Six cycles is 9 hours and five is 7 and a half; four cycles, 6 hours, falls short, and the calculator marks it that way.

Ninety minutes is an average. Real cycles run shorter or longer from person to person and through the night, so waking exactly between cycles is not something any calculator can promise. A regular schedule and enough total sleep do far more than precise timing.

Who this is wrong for

  • Shift workers and anyone sleeping in split blocks, whose cycles do not follow a single overnight pattern.
  • People with a sleep disorder such as insomnia or sleep apnea, where the problem is not the timing.
  • Teens and children. The AASM advises 8 to 10 hours for teens aged 13 to 18, and more for younger children, so the 7-hour mark on this page is too low for them.

Talk to a clinician when

  • You snore loudly, stop breathing or gasp in your sleep, or wake with headaches.
  • You feel very sleepy during the day even after enough time in bed.
  • Trouble falling or staying asleep has gone on for weeks and is affecting your days.

Read more

Sleep cycles explained: how long they last and how to time bed

Sources

  1. Patel AK, Reddy V, Shumway KR, Araujo JF. Physiology, Sleep Stages. StatPearls, NCBI Bookshelf, 2024.
  2. Paruthi S, et al. Recommended Amount of Sleep for Pediatric Populations: A Consensus Statement of the AASM. Journal of Clinical Sleep Medicine, 2016;12(6):785-786.
  3. Brain Basics: Understanding Sleep. National Institute of Neurological Disorders and Stroke.
  4. Watson NF, et al. Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the AASM and SRS. Journal of Clinical Sleep Medicine, 2015;11(6):591-592.

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This calculator gives an estimate for general education. It is not medical advice and it is not a substitute for care from a qualified clinician. Report an error to info@daliahealth.com.