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Sleep Cycle Calculator
Sleep comes in roughly 90-minute cycles. Waking up between cycles feels far more refreshing.
About sleep cycles
A full sleep cycle takes about 90 minutes. Waking up mid-cycle causes grogginess; waking at a cycle boundary feels lighter. This calculator counts in 90-minute blocks and adds ~14 minutes for the time it typically takes to fall asleep.
Most healthy adults need 5–6 full cycles (7.5–9 hours) a night. This is a general guideline, not a medical diagnosis — actual needs vary by person.