Sleep Calculator
Find the best bedtime for a wake-up time, or the best wake-up time for a bedtime, based on 90-minute sleep cycles.
Find your ideal sleep time
Choose what you know, then select a time.
Result
How this is calculated
Each full sleep cycle takes about 90 minutes. The calculator counts whole cycles back from a wake-up time (or forward from a bedtime), adding about 14 minutes for the time it typically takes to fall asleep.
How to use this calculator
- Choose whether you know your wake-up time or your bedtime.
- Select the time using the hour, minute and AM/PM fields.
- Press Calculate to see four options based on 3 to 6 full sleep cycles.
This tool provides general informational estimates only and is not a substitute for medical advice.
FAQ
Frequently asked questions
Why are sleep times based on 90-minute cycles?
A full sleep cycle (light sleep, deep sleep, REM) takes about 90 minutes. Waking up at the end of a cycle, rather than in the middle of one, generally feels less groggy.
Why is 14 minutes added for falling asleep?
It's a commonly cited average time for a healthy adult to fall asleep after getting into bed, so it's added to the bedtime calculation.
How many sleep cycles should I aim for?
5 cycles (about 7.5 hours) is a commonly cited target for adults, though individual needs vary.
Is this medical advice?
No. This tool gives general informational estimates only and does not replace advice from a doctor or sleep specialist.