Circumference Calculator

Calculate the circumference of a circle using the radius, diameter, or area with the calculator below.

How to Find the Circumference of a Circle

The circumference is the distance around a circle, also known as the perimeter of a circle. If the path around the circle were flattened out into a straight line, the line’s length would be the circumference.

Circumference Formulas

So “how do you go about solving circumference?” you might ask. Use these formulas to solve.

Given the Radius

Given the radius of a circle, the formula for circumference is:

C = 2πr

The circumference C is equal to 2 times pi times the radius of the circle r.

Given the Diameter

Given the diameter of a circle, the formula for circumference is:

C = πd

The circumference C is equal to pi times the diameter of the circle d.

Given the Area

Given the area of a circle, the formula for circumference is:

C = 2 × π × A ÷ π

The circumference C is equal to 2 times pi times the square root of the area of the circle A divided by pi.

How to Calculate the Diameter using the Circumference

It is possible to solve the diameter of a circle using the circumference. Since the diameter is equal to double the radius, use the inverse of the circumference formula to solve for the diameter.

d = C / π

Thus, the diameter d of a circle is equal to the circumference C divided by pi.

You might also be interested in our circle calculator for solving the other dimensions of a circle, including the radius, diameter, and area.