Sleep Cycle Calculator
Wake up between cycles, not in the middle of one.
Settings
Best = 5 or 6 full sleep cycles (7½ to 9 hours), which suits most adults. A sleep cycle is about 90 minutes.
How it works
Sleep runs in cycles of about 90 minutes. Waking at the end of a cycle usually feels easier than being pulled out of deep sleep. Most adults do well with 5–6 cycles (7.5–9 hours). The calculator adds the time you need to fall asleep (default 15 minutes).
Taking a nap? Keep it to about 20 minutes, or sleep a full cycle of 90 minutes. Waking somewhere in between often leaves you groggy.
These are estimates, not medical advice. Everyone's sleep differs, so adjust the settings to suit you.