## Circumference of a Circle Calculator

The circumference of a circle is the length of its perimiter. Since circles are difficult shapes measure (unlike rectangles and triangles), there is a slightly less obvious formula for finding their perimiter. The formula for calculating the circumference of a circle is the following: $$C = 2\pi r$$ Where $$r$$ is the radius of the circle and $$\pi$$ is the mathematical constant pi. If you are not familiar with the $$\pi$$ (pi) symbol, please visit this page: What is Pi?