Tools/Calculators/Circle Calculator
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Circle Calculator

Calculate a circle's diameter, circumference, and area from its radius.

Circle Calculator
Calculation result
Waiting for input

Input and result notes

Enter radius, not diameter. Circumference is 2πr and area is πr²; a radius in centimeters yields circumference in centimeters and area in square centimeters.

Calculators
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    Check whether three side lengths form a triangle and calculate its perimeter and area.

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    Convert areas between square meters, hectares, square kilometers, Chinese mu, and acres.