# 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:

## Physics

Chemistry

Biology

Science for Kids home page

History for Kids home page

Copyright 2012-2014 Karen Carr, Portland State University. This page last updated 2014.

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