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Our Sleep Calculator is designed to help you find the perfect time to fall asleep by factoring in 90-minute sleep cycles, plus an additional 15 minutes—the average time it takes to drift off.
Each sleep cycle lasts about 90 minutes, and most adults benefit from completing 5 to 6 cycles each night.
Why 5 or 6? Because adults typically need between 7 to 9 hours of sleep. Six full cycles equal 9 hours of restorative rest, while five cycles provide 7.5 hours.
Waking up in the middle of a sleep cycle can leave you feeling groggy and irritable. In contrast, waking up at the end of a cycle helps you start the day feeling refreshed and energized!