Sleep Calculator

Sleep runs in repeating cycles, and this tool plans a night around whole ones. Give it the time the alarm goes off and it returns bedtimes that finish a complete number of cycles, give it a bedtime and it returns the matching wake times, or enter both ends of a night to see the hours slept and how many cycles fit. Cycle length and the minutes you take to drop off are both yours to set, because ninety minutes is an average that varies by person and by night. It counts clock time only, so it cannot measure how well you slept or diagnose a sleep problem.

Calculator Type

Enter the time the alarm goes off and get the bedtimes that finish a whole number of cycles first.

Write it as 6:30 AM, 10:45 pm or 22:45.
Ninety minutes is the usual average. Anything from about 70 to 120 is normal.
Fifteen minutes is a common allowance. Use your own if you know it.
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Enter the time you are going to bed and get the wake times that land at the end of a cycle.

Write it as 6:30 AM, 10:45 pm or 22:45.
Ninety minutes is the usual average. Anything from about 70 to 120 is normal.
Fifteen minutes is a common allowance. Use your own if you know it.
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Enter both ends of the night to see the time in bed, the sleep it leaves and how many whole cycles fit.

Write it as 6:30 AM, 10:45 pm or 22:45.
Write it as 6:30 AM, 10:45 pm or 22:45.
Ninety minutes is the usual average. Anything from about 70 to 120 is normal.
Fifteen minutes is a common allowance. Use your own if you know it.
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