Sleep Cycle Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles.
About this Calculator
Sleep quality is determined by completing full 90-minute sleep cycles, not just total hours. Waking mid-cycle leaves you groggy even after 8 hours. This calculator finds optimal bedtimes (if you know your wake-up time) or optimal wake-up times (if you know your bedtime). Based on average 14-minute sleep onset time plus 90-minute cycles — aim for 5 or 6 full cycles for best rest.
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