## 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.

## What Is the Perimeter of a Circle Formula?

The perimeter of a circle formula has three components, two constants and one variable. The formula to calculate the perimeter of a circle or circumference formula can be given as:

**The perimeter of a circle ****= 2 π r **

= π D units

where,

r = radius of the circle

D = diameter of the circle

## Examples of Perimeter of Circle Formula

Let us solve some interesting problems using the perimeter of the circle formula.

**Example 1: Using the perimeter of a circle formula, calculate the circle’s circumference 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 the 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 circle’s radius circumference of 110 in.**

**Solution:**

To find: Radius of circle

Given: Circumference = 110 in

Using the perimeter of a circle formula,

The perimeter of the circle or circumference = 2π r

2 π r = 110

2 × 22/7 × r = 110

r = 110 × 7 / 44

r = 17.5

**Answer:** Radius of circle = 17.5 in.

**Example 3: The radius of a circle is 7 in. Using the perimeter of a circle formula, calculate the circle’s circumference.**

**Solution:**

To find: Perimeter of circle

Given: r = 7 in

The perimeter of circle formula = 2 π r

C = 2 × (22/7) × (7)

**Answer:** The circumference of a circle is 44 inches