How it works
Sleep runs in cycles of about 90 minutes. Waking between cycles helps you feel less groggy. We allow 15 minutes to fall asleep.
Frequently asked questions
How much sleep do adults need?
7–9 hours, which is five or six cycles.
Sleep Calculator
Find the best time to go to bed or wake up, in 90-minute cycles.
Your details
Go to bed at
9:45 PM
For 6 full cycles (9 hours)