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Sleep Cycle Calculator
EstimatorCalculate ideal wake-up or bedtimes based on 90-minute sleep cycles.
About This Tool
Sleep cycles last approximately 90 minutes, cycling through light sleep, deep sleep, and REM sleep. Waking mid-cycle causes grogginess (sleep inertia); waking at cycle end feels natural. Adults typically need 5–6 cycles (7.5–9 hours) per night.