About Sleep Calculator

Free tool to optimize your sleep schedule using 90-minute cycles. No ads, no signup - just simple math that works.

Why I Built This

I was tired of waking up groggy after 8 hours of sleep while sometimes feeling great after just 6 hours. Once I learned about sleep cycles, everything clicked. Quality sleep isn't just about hours - it's about timing. I built this tool to make sleep science accessible to anyone, not just sleep nerds like me.

The Science

This calculator uses the widely-accepted model of 90-minute sleep cycles. Each cycle takes you through light sleep, deep sleep, and REM sleep. Here's the trick: waking up at the end of a complete cycle (during light sleep) makes you feel refreshed. Wake up mid-cycle during deep sleep? You'll feel like you got hit by a truck.

Where the Numbers Come From

Age-based recommendations come from the CDC and National Sleep Foundation. They've done the research, I just made it easier to use. The 90-minute cycle thing? That's been studied for decades and it holds up.

Disclaimer

This tool is for informational purposes only - it's not medical advice. If you have serious sleep problems, talk to a doctor. This calculator helps with timing, but it won't fix underlying sleep disorders.