Sleep Calculator
Choose when you need to wake up or when you're going to bed, and get ideal sleep times based on complete 90-minute cycles. Waking between cycles leaves you groggy — this tool helps you avoid that.
Go to bed at one of these times:
Sleep cycles average approximately 90 minutes but vary between individuals. The 15-minute fall-asleep period is an average estimate.
This calculator provides estimates based on population-level formulas and is not a substitute for advice from a qualified health professional.
How it works
A typical sleep cycle lasts about 90 minutes and moves through light sleep, deep sleep, and REM stages. Waking up at the end of a complete cycle — rather than in the middle of one — tends to leave you feeling more alert and refreshed. This calculator counts backward or forward in 90-minute intervals to find those ideal transition points.
It also accounts for the average time it takes to fall asleep (about 15 minutes). So if you set a wake-up time of 7:00 AM, the suggested bedtimes factor in that buffer, giving you realistic times to actually get into bed.
Most adults need between 4 and 6 complete cycles (6 to 9 hours) per night. The tool highlights the recommended range while still showing shorter and longer options so you can make the best choice for your schedule.