About

What Is This Tool?

Sleep Cycle Calculator is a free tool that helps you find the best time to go to sleep or set your alarm based on your body's natural 90-minute sleep cycles. Waking at the end of a complete cycle — when sleep is lightest — means you rise feeling alert instead of groggy.

How Does It Work?

The calculator accounts for the average 14 minutes it takes adults to fall asleep, then calculates four wake-up or bedtime options based on 3, 4, 5, and 6 complete 90-minute cycles. The science behind sleep cycles is well-established in sleep research literature.

Who Built It?

This site was built by a small independent developer with the goal of making practical, science-backed tools freely available to everyone. No sign-up, no subscription, no cost.

Our Mission

Good sleep is one of the highest-impact things you can invest in for your health, mood, and performance. We built this tool to make the basics of sleep science easy to apply in real life.

Medical Disclaimer

This tool is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. If you have concerns about your sleep, consult a qualified healthcare provider.

Privacy

No personal data is collected or stored. All calculations run locally in your browser. See our Privacy Policy for full details.

Contact

Questions or feedback? Visit our contact page.