Sleep Calculator
Find the best times to go to bed or wake up, based on 90-minute sleep cycles.
Go to bed at one of these times
23:156 cycles · 9 h of sleep
00:455 cycles · 7 h 30 of sleep
02:154 cycles · 6 h of sleep
Assumes about 15 minutes to fall asleep.
How it works
Sleep happens in cycles of about 90 minutes. Waking up at the end of a cycle — rather than in the middle — helps you feel more rested. This tool suggests times for 4, 5 or 6 full cycles (6 h, 7 h 30 or 9 h), plus ~15 minutes to fall asleep.
Advertisement
Frequently asked questions
Why 90-minute cycles?
A full sleep cycle (light, deep and REM sleep) lasts about 90 minutes. Waking at the end of one, not in the middle, reduces grogginess.
How many cycles do I need?
Most adults feel best with 5 to 6 cycles per night (about 7.5 to 9 hours).