## Geometry and Trigonometry## Measurements and Transformations |

## What are the measurements of a circle? |

There are many measurements of a circle. The perimeter of a circle is actually called the *circumference;* to calculate this, multiply pi (π) times the diameter, *d* (π*d*), or pi (π) times twice the radius, *r* (2π*r*). The area of a circle is calculated by multiplying pi (π) times the radius squared, or π*r*^{2}.