How to Find the Area of a Circle

Finding the Area of a Circle

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

Start with the formula:

Area = πr2

Don't forget: π is pi (≈ 3.14) and r2 = r × r (r squared).

2

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

Area = π × 52 = π × 5 × 5 = 78.5 cm2

Answer:

The area of the circle with a radius of 5 cm is 78.5 cm2.

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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

See Also

What is a circle? What is pi? What is the radius? Find the area of a circle using the diameter What is the diameter? Find the area of a circle ( interactive widget)