Circle Area Calculator

Circle Area Calculator: Find circle area, circumference and diameter from a radius.

Circle Area Calculator

Circle Area Calculator: Enter the radius in any length unit. The result reports circle area in square units, with the circumference and diameter in matching length units.

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How to use Circle Area Calculator

Enter the radius in any length unit. The result reports circle area in square units, with the circumference and diameter in matching length units.

How Circle Area Calculator calculates the result

For radius r, area = πr², circumference = 2πr and diameter = 2r. Area uses square units while circumference and diameter retain the original length unit.

Example

A radius of 2 produces an area of about 12.566371 square units, circumference about 12.566371 units and diameter 4 units.

What to know

Assumes a perfect Euclidean circle. Displayed decimals are rounded; the internal calculations use JavaScript numeric precision.