Circumference of a Circle

Circumference of a Circle

How to solve the circumference of a circle problems: formulas, examples, and their solutions.

Formulas

C = 2*pi*r. C: circumference of a circle, r: radius of a circle, pi: 3.141592...

C = 2πr

C: circumference of a circle
r: radius of a circle
π: 3.141592...

C = pi*d. C: circumference of a circle, d: diameter of a circle, pi: 3.141592...

C = πd

C: circumference of a circle
d: diameter of a circle
π: 3.141592...

This is true because d = 2r.

Example 1

Find the circumference of the given circle. Radius: 5

r = 5

C = 2⋅π⋅5

Example 2

Find the circumference of the given circle. Diameter: 13

d = 13

C = π⋅13