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How to use Circle Calculator

Type any one known circle measurement and the tool instantly solves the radius, diameter, circumference and area with formulas.

Frequently asked questions

What can I enter to solve a circle?

Any single value — radius, diameter, circumference or area — and the calculator derives the other three.

What are the circle formulas used?

Area = πr², circumference = 2πr, and diameter = 2r; each is applied automatically from your input.

How accurate is pi in the results?

It uses JavaScript's built-in high-precision value of π, so results are accurate to many decimal places.

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