Sleep Calculator
Best bedtime & wake-up time
Go to bed at one of these times
Each sleep cycle lasts about 90 minutes. Five to six cycles (7.5–9 hours) is ideal for most adults.
About the Sleep Calculator
Sleep happens in cycles of roughly 90 minutes. Waking up in the middle of a cycle can leave you tired, while waking at the end of one feels much easier. Tell the calculator when you want to wake up or when you are going to bed, and it suggests times that line up with full sleep cycles.
- Choose “I want to wake up at” or “I'm going to bed at”.
- Pick a time, or press “Sleep now”.
- Choose one of the suggested times. Five or six cycles (7.5–9 hours) is ideal for most adults.
Frequently asked
How long is a sleep cycle?
About 90 minutes on average, although it varies from person to person and through the night.
Does the calculator include time to fall asleep?
Yes. It adds 15 minutes, the average time it takes to fall asleep. You can change this.
How much sleep do adults need?
Most adults need 7 to 9 hours per night. Teenagers need 8 to 10 hours.
Is what I type sent to a server?
No. The tool runs entirely in your browser and there's no server behind it, so what you type never leaves your device and nothing is stored. You can check: it keeps working if you go offline after the page has loaded.
More from the Calculators drawer
Other tools kept in this drawer, plus a few favourites from the bench.