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🔬 نیند Science

Each sleep cycle lasts approximately 90 minutes, cycling through NREM stages 1, 2, 3 and then REM sleep. Waking at the end of a complete cycle dramatically reduces sleep inertia (morning grogginess) compared to waking mid-cycle. This calculator finds bedtimes that align with 5, 6, 7, or 8 complete cycles.

Based on: Kleitman & Aserinsky (1953) · NSF Guidelines (2022) · Van Dongen et al. (2003)