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Sleep Calculator
Free sleep calculator using 90-minute sleep cycles. Enter your wake-up time or choose 'sleep now' to find the best bedtimes so you wake up refreshed, not groggy.
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How the Sleep Calculator works
This tool runs entirely in your browser — nothing you type is sent to a server, and there is no signup. Enter your input above and get an instant result.
Frequently asked questions
Is the Sleep Calculator free?
Yes. Every tool on Simple Sites is completely free to use, with no account required.
Does it work on mobile?
Yes. The page is fully responsive and works on phones, tablets, and desktops.
Is my data private?
The calculation happens client-side in your browser. We don't store your input. See individual tools for any external lookups they perform.