About SleepCalculator
SleepCalculator is a free tool that helps you time sleep around your body’s natural rhythm. Instead of guessing a bedtime, you pick when you want to wake up (or go to sleep) and we suggest times that line up with the end of a sleep cycle, so you wake feeling rested rather than groggy.
How the calculator works
Sleep runs in cycles that average about 90 minutes. The calculator counts those cycles forward or backward from the time you enter and adds roughly 15 minutes to account for the time it takes to fall asleep. It then shows several options, typically 4, 5, and 6 cycles, so you can choose how much total sleep fits your night.
Who is behind it
Content is maintained by the SleepCalculator Editorial Team. We write in plain language, link to primary sources, and update guidance when expert recommendations change. Our goal is practical scheduling help, not medical advice.
Our sources
The sleep guidance on this site is based on public, authoritative sources, including:
A note on medical advice
SleepCalculator is for general information and scheduling only. It is not a substitute for professional care. If you have ongoing trouble sleeping, loud snoring, or daytime exhaustion, talk to a doctor. These can be signs of a treatable sleep disorder.
Questions or corrections? Contact us.