Sleep Cycle Calculator

Counts whole 90-minute sleep cycles from your target time and adds ~15 minutes to fall asleep. From a wake time it counts backward to bedtimes; from a bedtime it counts forward to wake times. Five to six cycles (7.5–9 hours) is the recommended range.

Carskadon MA & Dement WC, sleep-cycle architecture; National Sleep Foundation sleep-duration recommendations.

Cycle length varies from about 80–110 minutes and drifts across the night, so these are targets rather than exact times. Total sleep and consistency matter most.

Diagnosing or treating sleep disorders. Persistent insomnia, loud snoring, or daytime exhaustion deserve a conversation with a doctor.

Sleep runs in cycles of roughly 90 minutes, moving from light to deep to REM sleep and back. Waking at the end of a cycle — rather than mid-cycle — tends to feel far easier. This calculator counts whole 90-minute cycles from your wake time or bedtime and adds time to fall asleep.

Most adults do best with five to six cycles a night, which works out to about 7.5–9 hours of sleep. Four cycles (6 hours) can work in a pinch, but consistently short sleep hurts recovery, mood, and health.

Because falling asleep isn't instant. The calculator assumes about 15 minutes of sleep latency by default, so the times account for the gap between getting into bed and actually drifting off.

No. Cycle length varies from roughly 80 to 110 minutes between people and even drifts across the night. Treat these times as helpful targets, not stopwatch-exact rules — total sleep and consistency matter more than hitting a precise minute.

A consistent schedule, morning light exposure, a cool dark room, and limiting caffeine and alcohol late in the day all improve sleep quality. Waking at the same time every day — even weekends — is one of the most powerful habits for feeling rested.