Sleep Calculator
Calculate the best time to sleep or wake up based on 90-minute sleep cycles. Wake up refreshed, not groggy.
I need to wake up at:
Go to sleep at one of these times:
09:45 PM
6 sleep cycles · 9.0 hours
Recommended
11:15 PM
5 sleep cycles · 7.5 hours
12:45 AM
4 sleep cycles · 6.0 hours
Based on 90-minute sleep cycles + 15 minutes to fall asleep. Waking between cycles helps you feel refreshed.
Adults need 7-9 hours of sleep (4-6 cycles).