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Circle Calculator — Free Online Calculator

Circle Calculator solves A = πr², C = 2πr — A = area, C = circumference, r = radius. Enter your known values and the calculator solves for the rest instantly. All processing happens client-side in your browser, with nothing sent to a server. Free, unlimited, and no registration needed.

How to use Circle Calc

1. Enter your known values in the fields.
2. The result updates instantly as you type.
3. Copy or note down the result.

Frequently asked questions

What formula does Circle Calculator use?

A = πr², C = 2πr — A = area, C = circumference, r = radius.

Can I use it on my phone?

Yes. The layout adapts to small screens and behaves the same on mobile as on desktop.

Is my input saved anywhere?

No. Values stay in your browser and are gone as soon as you close the tab.

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