## The Lesson

The area of a circle is found using the formula:In this formula,

**r**is the radius of the circle. The image below shows what we mean by radius:

## How to Find the Area of a Circle

Finding the area of a circle is easy.## Question

What is the area of a circle with a radius of 5 cm, as shown below?## Step-by-Step:

# 1

# 2

Substitute the radius into the formula. In our example, r = 5.

Area = π × 5

^{2}= π × 5 × 5 = 78.5 cm^{2}## Answer:

The area of the circle with a radius of 5 cm is 78.5 cm^{2}.

## "Find the Area" Widget

## How to Find the Area of a Circle Using the Diameter

The area of a circle can be found using the diameter rather than the radius. The area of a circle, using the diameter, is found using the formula:In the formula,

**d**is the diameter of the circle. The image below shows what we mean by diameter:

Read more about how to find the area of a circle using the diameter

## What Is a Circle?

A circle is a shape containing a set of points that are all the same distance from a given point, its center.## Radius and Diameter

The diameter of a circle is twice the length of its radius. If you are given the diameter of a circle, halve it to find the radius and put this in the formula. Alternatively, use the formula containing diameter.## What Is Pi?

**π**is the symbol for pi.

**π**is how many times longer a circle's circumference is than its diameter. It is the circumference divided by the diameter:

**π**is the same for all circles, and is approximately equal to 3.14.

## A Note on Units

The area of a circle is a length times a length, so we say its dimension is length^{2}. (All areas are lengths squared). This affects the units used. If the radius is in cm, the area is in cm

^{2}. If it is in inches, the area is in inches

^{2}.