Circumference and Area of a Circle

Just as the perimeter of a polygon is the distance around the polygon, the circumference of a circle is the distance around the circle.

The ratio of the circumference C of a circle to its diameter d appears to be a number slightly greater than 3, regardless of the size of the circle. The ratio of the circumference of a circle to its diameter is always fixed and equals an irrational number called pi or π.

Properties of a circumference:

  1. The circumference is the distance around a circle.
  2. The circumference around a circle is often represented by the letter C.
  3. The ratio between the circumference of a circle and its diameter is about 3:1. For each diameter, circumference is a little more than 3.
If a circle has an area of A square units and a radius of r units, then A = πr².

Find out more about the circumference and area of a circle.

Circumference and Area of a Circle


Practice: Solve problems involving circumferences of circles in the following exercises.

Circumference and Area of a Circle 1

Circumference and Area of a Circle 2

Circumference and Area of a Circle 3