How to Find the Area of a Triangle

Finding the Area of a Triangle

The area of a triangle is found using the formula:

In this formula, b is the length of the base of the triangle and h is the height of the triangle. The image below shows what we mean by the lengths of the bases and the height:

Interactive Widget

Use this interactive widget to create a triangle and then calculate its area. Start by clicking in the shaded area.




Oops, it's broken!

Turn your phone on its side to use this widget.

How to Find the Area of a Triangle

Finding the area of a triangle is easy.

Question

What is the area of a triangle with a base of 5 cm and a height of 3 cm, as shown below?

Step-by-Step:

1

Start with the formula:

Area = ½bh

Don't forget: ½bh = ½ × b × h

2

Substitute the length of the base and the height into the formula. In our example, b = 5 and h = 3.

Area = ½ × 5 × 3 = 7.5 cm2

Don't forget: ½ × a number = 0.5 × a number = a number ÷ 2.

Answer:

The area of the triangle with a base of 5 cm and a height of 3 cm is 7.5 cm2.

Slider

The slider below shows another real example of how to find the area of a triangle.

Open the slider in a new tab

How to Find the Area of a Triangle Using Trigonometry

The area of a triangle can also be found using trigonometry.

The area is found using the formula:

In the formula, a and b are lengths of two sides of the triangle and C is the angle between them. The image below shows what we mean by the two sides and the angle between them:

Read more about how to find the area of a triangle using trigonometry

See Also

What is a triangle? Find the area of a triangle using trigonometry What is trigonometry? What is an angle? What are the types of triangles? Equilateral triangles Isosceles triangles Scalene triangles