Sleep Calculator
Calculate your optimal wake-up times and bedtimes using 90-minute sleep cycles (NREM + REM) and age recommended ranges.
Quick Summary: Sleep Calculator
The human brain sleeps in 90-minute cycles. Waking up in the middle of a cycle causes 'sleep inertia' (grogginess). Waking up at the end of a cycle (e.g., after 7.5 or 9 hours) leaves you feeling alert.