Questions
How long is a sleep cycle?
About 90 minutes on average, usually between 70 and 120 minutes. A night is typically four to six cycles of light, deep and REM sleep.
Why wake up at the end of a cycle?
Waking from deep sleep often leaves you groggy. At the end of a cycle sleep is lighter, so waking up is usually easier.
How many hours of sleep do I need?
Most adults need 7 to 9 hours a night, which is five or six cycles. Teenagers and children need more.
What is the time to fall asleep?
It is how long it takes you to fall asleep after going to bed. For most people it is 10 to 20 minutes; the calculator starts at 15.