Our circle area calculator is used to find the area of a circle given its radius, diameter or circumference. Just enter the measurement you know. Then tap or click the Calculate button. You can also select units of measure for both input data and results. The area of a circle will be shown in the selected units. You will also receive a detailed stepwise solution.
Note: Most calculators and programs show too big and too small results in scientific notation. And so does this circle area calculator. It uses the number π accurate to 15 decimal places. This enhances its computational accuracy.
Formulas for finding the area of a circle:
Given the Radius
A = πr2
Given the Diameter
A = πD2/4
Given the Circumference
A = C2/(4π)
where A is Area; r is Radius; D is Diameter; C is Circumference; π (pi number) is a mathematical constant ≈ 3.141592653589793