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Sleep Calculator
Calculate the best bedtime or wake-up time based on 90-minute sleep cycles.
About This Calculator
Human sleep architecture progresses through 90-minute cycles of light sleep, deep sleep, and REM sleep. Waking at the end of a cycle (rather than mid-cycle) reduces sleep inertia. The CDC recommends 7–9 hours for adults; chronic short sleep (< 6 hours) is linked to metabolic disease, immune dysfunction, and cognitive decline.