Sleep Cycle Calculator
Find the best bedtimes or wake times based on 90-minute sleep cycles.
Go to bed at one of these times:
21:4623:1600:4602:16
How to use
Enter your values above and read the result instantly.
How it works
Everything is computed locally in your browser — nothing is uploaded.
Frequently asked questions
Is it free?
Yes, completely free with no limits.
Is my data private?
Yes, all processing happens in your browser.