Sleep Cycle Calculator

The best times to fall asleep or wake up so you finish a full sleep cycle.

min
The average adult takes 10-20 minutes.
9:46 PMGo to bed for 6 cycles (9 h of sleep)
11:16 PMGo to bed for 5 cycles (7.5 h of sleep)
Go to bed for 4 cycles (6 h of sleep)
12:46 AM
Go to bed for 3 cycles (4.5 h of sleep)
2:16 AM

Times include 14 minutes to fall asleep. Waking at the end of a 90-minute cycle feels easier than waking in deep sleep.

About the Sleep Cycle Calculator

Sleep is not uniform. Through the night you move through cycles of light sleep, deep sleep and REM that last roughly 90 minutes each. Waking at the end of a cycle, when sleep is light, usually feels refreshing; an alarm that fires in the middle of deep sleep leaves you groggy even after a long night. This calculator counts backwards from your wake-up time (or forwards from bedtime) in whole cycles, adding the minutes you typically need to fall asleep.

Most adults need five to six cycles (7.5 to 9 hours). The tool highlights those, but also shows the three- and four-cycle options for nights when a full sleep is not possible: a shorter sleep aligned with a cycle boundary often beats a slightly longer one that is cut mid-cycle.

Cycle length varies between people and across the night, so treat the suggested times as a starting point and adjust by 10-15 minutes if you consistently wake tired.

How to use the Sleep Cycle Calculator

  1. Choose whether you know your wake-up time or your bedtime.
  2. Enter that time and how long you usually take to fall asleep.
  3. Pick one of the suggested times: five or six cycles are best for most adults.

Frequently asked questions

How long is a sleep cycle?

About 90 minutes on average, ranging from 70 to 120 minutes. The first cycles of the night contain more deep sleep; later cycles contain more REM sleep.

How many hours of sleep do adults need?

Most adults need 7 to 9 hours, which is five to six full cycles. Teenagers need 8 to 10 hours and young children considerably more.

Why do I feel worse after 8 hours than after 7.5?

Eight hours is not a whole number of 90-minute cycles, so an alarm may interrupt deep sleep. 7.5 hours (five cycles) or 9 hours (six cycles) often feel better.

Does the calculator account for the time to fall asleep?

Yes. The default 14 minutes is the average for healthy adults. If you tend to lie awake longer, increase the value so the suggested bedtime moves earlier.