Holistic Health
Sleep Cycle Calculator
Waking up at the right time in your sleep cycle is the difference between feeling rested and feeling wrecked. Enter your bedtime to find your optimal wake-up windows.
Accounts for ~14 minutes to fall asleep
The 90-Minute Rule
Sleep researchers have identified that human sleep naturally organizes itself into approximately 90-minute cycles. Each cycle moves through light sleep, deep sleep, and REM sleep. At the end of each cycle, there is a brief period of very light sleep — almost wakefulness — before the next cycle begins.
Waking during this light period, rather than being pulled from deep sleep by an alarm, is what determines whether you wake feeling alert or groggy. The 90-minute figure is an average — individual cycle length varies from about 80 to 100 minutes — but it is accurate enough to be genuinely useful for planning your sleep schedule.