What is the formula for the perimeter of a circle?

2 x pi x r where pi = 3.1416

or

pi x diameter.

To find the perimeter you do pi (3.1415) times the diameter.

Or you can figure by the radius (P=2 π r; i.e. Perimeter = 2 x 3.1415 x radius)

The perimeter of a circle is its circumference. We use these formulas to find the circumference of a circle;

• C=d times pi or
• C=2 times the radius times pi (3.14).

To make it easier to explain:

Area: Pi (3.14) X Radius Squared (r 2) from the center out of the circle

Perimeter: Pi (3.14) X Diameter (d) from one side of the circle to the other

The perimeter of a circle is called Circumference.

Here is the formula for Circumference:

C= pi x d (pi times diameter)

C= 3.14 x ______ (fill in the blank with the diameter of the circle)

C= (your answer)

NOTE: Pi is approximately 3.14 so when you are using pi to multiply, replace it with 3.14

When the diameter is not given in a circle, double the radius to find the length of the diameter.