Health & FitnessFree
Sleep Calculator
Find the best times to wake up or go to sleep based on 90-minute sleep cycles.
Go to sleep at:
9:45 PMRecommended
9.0h sleep
6 cycles
11:15 PM
7.5h sleep
5 cycles
12:45 AM
6.0h sleep
4 cycles
2:15 AM
4.5h sleep
3 cycles
These times account for ~15 minutes to fall asleep. Each sleep cycle is 90 minutes.
How it works
Enter the time you need to wake up (or the time you plan to sleep) and the sleep calculator generates a list of optimal bedtimes or wake-up times based on 90-minute sleep cycles plus an average 15-minute time to fall asleep.
Why use this tool?
Waking up at the end of a sleep cycle — rather than in the middle — leaves you feeling refreshed instead of groggy. This free sleep cycle calculator is used by students, shift workers, and anyone optimizing their sleep quality.