Perimeter of a Circle Formula
The perimeter of a circle formula is used to find the perimeter of a circle. The perimeter of a circle is its boundary or the complete arc length of the periphery of a circle. The term that denotes the perimeter of a circle is called its circumference. Hence the perimeter of a circle tells us about the circumference of a circle, therefore it is also known as the circumference of a circle formula. Let us learn more about the perimeter of the circle formula along with solved examples.
What is the Perimeter of a Circle Formula?
The perimeter of a circle formula has three components, 2 constants and one variable which is the radius of the circle. The formula to calculate the perimeter of a circle or circumference formula can be given as:
Perimeter of a circle = 2 π r = π D
where,
 r = radius of the circle
 D = diameter of the circle

Example 1: Using the perimeter of a circle formula, calculate the circumference of the circle with a diameter of 7 in (Use the value of π as 22/7)?
Solution:
To find: Perimeter of a circle
Given: Diameter of circle = 7 in
Using perimeter of a circle formula,
The perimeter of a circle = π D
Perimeter or circumference = 22/7 × 7
= 22 in
Answer: Perimeter of circle or circumference = 22 in.

Example 2: Using the perimeter of a circle formula, find the radius of the circle having a circumference of 110 in.
Solution:
To find: Radius of circle
Given: Circumference = 110 in
Using perimeter of a circle formula,
The perimeter of the circle or circumference = 2 π r
2 π r = 110
2 × 22/7 × r = 110
r = 110 × 7 / 44
r = 17.5
Answer: Radius of circle = 17.5 in