Circumference

Circumference of a circle

In geometry, circumference is the distance around a closed curve; for example, a circle. It is a special kind of perimeter. The length of the circumference of a circle is often written as [math]\displaystyle{ C }[/math],^[1] with:^[2]^[3]

[math]\displaystyle{ C= \pi d }[/math]

where d is the diameter of the circle.

Circumference Media

  circumference C
*
  diameter D
*
  radius R
*
  center or origin O
Circumference = $π$ × diameter = 2 $π$ × radius.
When a circle's diameter is 1, its circumference is \pi.
When a circle's radius is 1—called a unit circle—its circumference is 2\pi.