The circumference formula of a circle: L=2πr or L=πD(D is the diameter of the circle).

Extended data:

In a plane, a closed curve formed by a moving point rotating around a certain point with a certain length is called a circle. A circle has countless points.

On the same plane, the set of points whose distance to a fixed point is equal to a fixed length is called a circle. A circle can be expressed as a set {m |||| mo | = r}, and the standard equation of a circle is (x-a)? + (y - b)？ = r？ . Where (a, b) is the center of the circle and r is the radius.

References:

Baidu encyclopedia _ circle