Sleep calculator
Choose when you need to wake up to see when to go to bed, or when you go to bed to see the best times to wake up.
Frequently asked questions
Why 90-minute cycles?
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 deep sleep, usually feels easier. Real cycles vary from about 70 to 120 minutes.
How much sleep do adults need?
Seven to nine hours a night for most adults, which is five or six cycles. Teenagers need eight to ten.
What is the 15 minutes for?
The average time it takes to fall asleep. Change it if you usually fall asleep faster or slower.