How do you calculate the area of a circle?

Square the radius and multiply by π: area = πr².

Worked example

For a diameter of 10 cm, the radius is 5 cm and area is 25π, approximately 78.54 cm².

Try it with your own numbers

Use the Circle Calculator to check another example. Read the input labels carefully and keep units consistent.

Before you use the answer

Choose the correct starting quantity and keep full precision until the final step. An arithmetic result describes the numbers entered; the usefulness of the result depends on accurate measurements and the assumptions in the calculation.