Sleep Calculator
Best bedtime or wake-up time based on 90-min sleep cycles
Use this when you need a fast, accurate result — no sign-up, works entirely in your browser.
4 cycles (6 h)—
5 cycles (7.5 h)—
6 cycles (9 h)—
7 cycles (10.5 h)—
How to Use
- Enter your details into the fields above.
- Click the calculate button to get your result instantly.
- Use the clear button to start a new calculation.
Example
- Wake at 07:00 → 5 cycles (7.5 h): bedtime ≈ 23:30; 6 cycles (9 h): bedtime ≈ 22:00
- Wake at 07:00, plan 4 sleep cycles → Best bedtimes: 20:30, 22:00, 23:30, or 01:00
Formula
Sleep runs in roughly 90-minute cycles. Sleeping a whole number of cycles (typically 5-6) means you wake between cycles and feel more refreshed.
About Sleep Calculator
Best bedtime or wake-up time based on 90-min sleep cycles. This free online tool gives you fast, accurate results without registration or downloads.
Everything runs locally in your browser, so your data is never uploaded or stored — privacy first.
Frequently Asked Questions
Is this tool free to use? +
Yes, it is completely free with no registration or download required.
Is my data private? +
Yes. Everything is processed locally in your browser. Nothing is uploaded or stored on our servers.
Does it work on mobile? +
Yes, it works on any device — phone, tablet, or desktop.