Time & Date
Sleep Time Calculator
Find what time to go to bed, given a wake-up time and desired hours of sleep.
The result is the time to go to bed so that the wanted hours of sleep fit before the wake-up time entered.
Formula
Bedtime = wake-up time minus desired sleep duration, wrapped around the 24-hour clock.
How it works
Enter the time you must wake up and how many hours of sleep you want. The calculator subtracts the sleep duration and gives the bedtime, wrapping past midnight where needed.
Worked example
For example, waking at 07:00 and wanting 8 hours of sleep gives a bedtime of 23:00, since 07:00 minus 8 hours is 23:00 on the previous evening.
FAQs
Does it include time to fall asleep?
No. It counts sleep itself only; if you usually take time to fall asleep, go to bed that much earlier.
What if I want 7.5 hours?
Fractional hours work: 7.5 hours is 7 hours 30 minutes.
Is this medical advice?
No. It is a simple time calculation; sleep needs vary by person.
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