How to Find the Area of a Trapezoid

Finding the Area of a Trapezoid

The area of a trapezoid is found using the formula:

In this formula, b1 and b2 are the lengths of the bases of the trapezoid and h is the height of the trapezoid. The image below shows what we mean by the lengths of the bases and the height:

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




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How to Find the Area of a Trapezoid

Finding the area of a trapezoid is easy.

Question

What is the area of a trapezoid with bases of length 3 cm and 5 cm and a height of 2 cm, as shown below?

Step-by-Step:

1

Start with the formula:

Area = ½(b1 + b2)h

Don't forget: ½(b1 + b2)h = ½ × (b1 + b2) × h

2

Substitute the length of the bases and the height into the formula. In our example, b1 = 3, b2 = 5 and h = 3.

Area = ½ × (3 + 5) × 2

Area = ½ × (8) × 2

Area = 8 cm2

Don't forget: Calculate what's in the brackets () first (using the order of operations). In our example, (3 + 5) = 8.

or: ½ × a number = 0.5 × a number = a number ÷ 2.

Answer:

The area of a trapezoid with bases of length 3 cm and 5 cm and a height of 2 cm is 8 cm2.

Slider

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

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See Also

What is a trapezoid?