Enter a wake-up time or bedtime to see several options for the other, timed to complete full 90-minute sleep cycles so you wake up feeling rested rather than groggy.
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A full sleep cycle lasts about 90 minutes, moving through light sleep, deep sleep and REM sleep. Waking up in the middle of a cycle (especially during deep sleep) tends to feel groggy, while waking up at the end of a complete cycle tends to feel more refreshed. This calculator works in 90-minute increments from your entered time, and adds about 15 minutes for the average time it takes to fall asleep.
Everyone's ideal sleep duration varies, most adults need 4 to 6 complete cycles (6 to 9 hours) per night. Showing multiple cycle-count options lets you pick a bedtime or wake-up time that both fits your schedule and lands at the end of a complete cycle.
Most adults feel best with 5 to 6 complete cycles (7.5 to 9 hours) per night, though this varies by individual. Fewer than 3-4 cycles is generally considered insufficient sleep for most adults.
It typically takes the average person about 15 minutes to fall asleep after getting into bed, this calculator accounts for that so the cycle timing starts from when you're actually asleep, not just from when you lie down.
No, actual sleep cycle length varies somewhat by individual, typically 70-120 minutes. 90 minutes is a widely used average for general planning purposes.
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