Sleep Calculator
Calculate the best times to fall asleep or wake up based on 90-minute sleep cycles. Waking up between cycles helps you feel more rested and alert.
How to Use
Choose whether you want to calculate bedtimes based on a desired wake-up time, or wake-up times based on when you plan to go to sleep. Enter your time and click Calculate. The calculator shows 6 optimal times, each representing a different number of complete sleep cycles (4 to 6 cycles). Times highlighted in green are the recommended options for most adults (5–6 cycles, or 7.5–9 hours of sleep).
How It Works
Sleep Cycle = 90 minutes
Time to Fall Asleep = ~14 minutes
Optimal Sleep = 5–6 full cycles (7.5–9 hours)
A complete sleep cycle lasts about 90 minutes and includes light sleep, deep sleep, and REM sleep. Waking up at the end of a cycle — rather than in the middle — leaves you feeling refreshed instead of groggy. The calculator adds 14 minutes to account for the average time it takes to fall asleep. Most adults need 5 to 6 complete cycles per night for optimal health.