# Circumference

The circumference of a circle is the length of its perimeter.

Circumference is a middle school-level concept. It is listed in the California State Standards for Grade 6.

### Prerequisites

Circle: | A circle is the set of points in a plane that are equidistant from a given center point. |

Perimeter: | The perimeter is a length around the boundary of a closed two-dimensional region. The perimeter of a circle is called its circumference. |

Pi: | Pi is the mathematical constant defined as the ratio of the circumference of a circle to its diameter with value of approximately 3.14159. |