Circumference - Geometry for Kids - What is the circumference of a circle? How do we know the circumference if we only have the radius of a circle?

Circumference of a Circle

Radius
Circumference of a circle

The circumference of a circle is the distance all the way around the circle. It's the same as the perimeter, but a special word that we only use for the perimeter of a circle. The circumference is always equal to twice the radius of the circle times π (pi), or 2πr.

Click here to see a proof that this is always true for any circle.

Radius
Diameter
Area of a Circle
Main Geometry page

To find out more about circles, check out these books from Amazon.com or from your library:

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