Sleep Calculator
We sleep in cycles of about 90 minutes, and waking at the end of a cycle leaves you feeling refreshed rather than groggy. This calculator works out the best times to go to bed for a chosen wake-up time, or the best times to wake if you go to sleep now, counting through full sleep cycles.
Sleep Calculator
How the sleep calculator works
Sleep runs in roughly 90-minute cycles. Waking at the end of a cycle feels far better than waking in the middle. The calculator counts back from your wake-up time in full cycles — plus about 15 minutes to fall asleep — to suggest the best bedtimes, or forward from now to suggest wake-up times.
Tip
Aim for five or six cycles (7.5 to 9 hours) and keep a regular schedule to feel your most rested.
Frequently asked questions
How long is a sleep cycle?
A full sleep cycle lasts about 90 minutes and moves through light sleep, deep sleep and REM. Most people need five or six cycles a night.
Why wake up at the end of a sleep cycle?
Waking at the end of a cycle, in light sleep, feels natural and refreshing, while waking mid-cycle from deep sleep leaves you groggy.
How many hours of sleep do I need?
Most adults need 7-9 hours, which is about five to six 90-minute cycles. The calculator targets full cycles so you wake up at a good point.
How long does it take to fall asleep?
On average about 15 minutes, which the calculator adds before the first cycle so the suggested times are more realistic.
What is the best time to go to bed?
Choose a bedtime that gives you five or six full cycles before your wake-up time, and keep it consistent every night for the best rest.