Sleep Calculator
Find the best bedtime or wake-up time · free, no signup
Go to bed at one of these times
Free Sleep Cycle Calculator
Sleep runs in cycles of about 90 minutes. Waking in the middle of a cycle leaves you groggy, while waking at the end feels natural. Tell the calculator when you need to wake up and it suggests the bedtimes that complete whole cycles.
You can also enter a bedtime, or use 'sleep now', to see the best wake-up times. The calculation allows about 15 minutes to fall asleep.
Cycle-based
Times aligned to 90-minute cycles.
Two modes
Find bedtime or find wake-up time.
Sleep now
Best wake times if you go to bed now.
Adjustable
Change the time to fall asleep.
How to use it
- Choose whether you want a bedtime or wake-up time.
- Enter your time.
- Pick one of the suggested times.
- Set your alarm.
Frequently asked questions
How many hours of sleep do I need?
Most adults need 7 to 9 hours, which is 5 to 6 full sleep cycles.
What is a sleep cycle?
A repeating pattern of light, deep and REM sleep that lasts roughly 90 minutes.
Why allow 15 minutes to fall asleep?
That is the average time most people need to drift off.
Is this medical advice?
No. It is a planning aid. Talk to a doctor about sleep problems.