Circumference is the distance around a circle. That is, the circumference would be the length of the circle if it were opened up and straightened out to a line segment.

Radius is the distance from the center to the circumference of a circle.

**Formula to calculate circumference of a circle:**

Where, r is the radius of the circle

and π is a constant estimated to be 3.142 or

**Example:**

Calculate the circumference of a circle whose radius is 21 cm. (use π = 3.142)

Hence, the circumference of the circle is 131.964 cm.