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Circle Calculator
Calculate the radius, diameter, circumference, and area of a circle.
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Calculate the radius, diameter, circumference, and area of a circle.
Enter any value to calculate the others.
Enter values to visualize
Instantly determine the radius, diameter, circumference, and area of any circle by entering just one known dimension.
C = 2πr, A = πr²The relationship between a circle's core components is constant, defined by the mathematical constant Pi (π), which is approximately 3.14159.
You can find the radius by dividing the area by Pi (π) and then taking the square root of the result: r = √(A / π).
Our tool uses the standard JavaScript Math.PI constant (approx. 3.141592653589793) for calculations, providing results far more accurate than manual estimates.
Yes. The calculator is unit-agnostic; if you enter dimensions in inches, all resulting values will correspond to inches (or square inches for area).
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