Sleep Calculator
Find the best time to wake up or go to sleep
We'll calculate wake-up times from right now.
Based on 90-minute sleep cycles + 14 minutes to fall asleep
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How It Works
Your sleep naturally moves through cycles of light sleep, deep sleep, and REM — each cycle lasting roughly 90 minutes. Waking up at the end of a cycle, rather than in the middle of deep sleep, is why some mornings you spring out of bed and others you feel groggy despite a full night's rest. ZZZCalc uses the standard 90-minute cycle model plus an average of 14 minutes to fall asleep to pinpoint the ideal bedtimes or wake-up times for you. Aim for 5 or 6 complete cycles (7.5 to 9 hours) for the best restoration. If your schedule demands less, 4 cycles (6 hours) is preferable to waking mid-cycle. Consistency matters too — going to bed and rising at the same time each day reinforces your circadian rhythm, making it easier to fall asleep and wake up naturally without an alarm.