If I go to bed at 11:00 PM, when should I wake up?

How the sleep calculator works

Sleep runs in cycles of light, deep, and REM sleep that last about 90 minutes on average. Waking at the end of a cycle, rather than in the middle of deep sleep, tends to feel less groggy. The calculator counts back (or forward) in 90-minute cycles and adds about 15 minutes, the typical time it takes to fall asleep.

How much sleep do you need?

The American Academy of Sleep Medicine recommends that adults get 7 or more hours of sleep a night on a regular basis. For most people that means five or six cycles. Four cycles (6 hours) is fine now and then but too short as a habit.

Treat the times as a starting point

Cycle length varies from person to person and through the night, and the calculator can’t know how long you take to fall asleep. If you still wake up groggy, shift your bedtime 15 minutes earlier or later for a week and see how you feel. A consistent wake-up time, even on weekends, matters more than hitting an exact minute.

If you regularly lie awake for 30 minutes or more, or wake in the night and can’t get back to sleep, the problem may be insomnia rather than timing. That is worth raising with a clinician.

Work nights or early mornings? See our sleep schedules for shift workers.