Sleep Cycle Calculator

Human sleep follows approximately 90-minute cycles alternating between light sleep (REM) and deep sleep (non-REM). Sleep science research shows that waking at the end of a complete cycle leads to feeling refreshed, while waking during deep sleep causes grogginess and fatigue.

This tool incorporates both the 90-minute sleep cycle and the average sleep onset latency of about 14 minutes — the time it takes to actually fall asleep after getting into bed. The recommended sleep duration is 4-6 cycles (6-9 hours). The calculator works in both directions: enter your desired wake time to find optimal bedtimes, or enter your bedtime to find the best wake-up times.

Optimize your sleep schedule with science-based calculations. Useful for improving sleep quality, waking up refreshed, and establishing a healthy daily rhythm.