Sleep Calculator
When to go to bed to wake up at a given time, or when to wake up if you go to bed now, in whole sleep cycles
Enter a time, such as 07:00.
min
Enter from 0 to 120 minutes.
Go to bed at
Outlined: 7 to 9 hours of sleep, what adults need.
Sleep comes in cycles of about 90 minutes, light sleep, then deep sleep, then dreams. Waking at the end of a cycle, in light sleep, is easier than in the middle of deep sleep, so the times above are whole cycles away, plus the time it takes you to fall asleep.
A cycle lasts 70 to 120 minutes depending on the person and the night, so take these times as a guide. Teenagers need 8 to 10 hours.