About

Hi there! 👋

I built thesleepcyclecalc because I was tired of waking up tired. Like a lot of people, I assumed the answer was just “more sleep.” But even when I got 8 hours, I’d still wake up feeling groggy and disoriented.

Then I learned about 90-minute sleep cycles. The idea is simple: your brain cycles through light sleep, deep sleep, and REM sleep in roughly 90-minute blocks. Wake up at the end of a cycle, and you feel refreshed. Wake up mid-cycle — especially during deep sleep — and you feel terrible, no matter how many hours you were in bed.

The math was straightforward, but doing it manually every night was tedious. So I built this calculator — a quick, free tool that does the calculation for you.

The Science

The average human sleep cycle lasts 90 minutes (with individual variation ranging from 70-120 minutes). Most people complete 4-6 cycles per night, which translates to 6-9 hours of sleep.

The calculator assumes a standard 90-minute cycle and adds 15 minutes for the average time it takes to fall asleep (sleep latency). It’s based on established sleep science, not a fad — but everyone’s body is different. Use it as a starting point and adjust based on how you feel.

What's Next

This site is growing. I’m building more tools and writing evidence-based articles about sleep — including baby sleep schedules, shift worker calculators, and nap planners. If there’s a tool you’d find useful, I’d love to hear about it.

You can reach me at privacy@thesleepcyclecalc.com.