Math & Geometry · Runs in your browser

Circle Area and Circumference

Calculate area, circumference and diameter from a radius.

Enter values, or load the example to try this tool.

Result

Input rules and method

Radius must be positive. Area = πr², circumference = 2πr and diameter = 2r. Results use your input unit and square units for area.

How to use this tool

Enter your values, or choose Load example to see a complete starting point.
Choose Run tool. If an input is invalid, read the message beside the result and correct it.
Review the output, then copy it or download a file. Keep original inputs if you need to repeat the task.

Privacy and limits

Processing happens on your device. This workspace does not send your inputs to a processing server or save them. Text inputs are limited to 100,000 characters; output is limited to 1,000,000 characters to keep the page responsive. Other limits are explained above.

Can I try this without an account?

Yes. Load example provides a working input, and no signup is required. Favourites save only the tool name on this browser.

Why does my input show an error?

Check the input rules above, especially the allowed range, separators and supported format. The result box is cleared on an error so an old result is not mistaken for a successful new run.

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Try a sample or see input tips

Start small, review the output, then use your own input. Sample files contain synthetic data.

For file tools, download the sample first, then select it with the tool’s upload control. Your own file is never replaced automatically.

Keep going with your next task

Choose a related next step. Copy any result you want to reuse; opening a tool does not transfer your inputs.