How To: Determine the area of a trapezoid

Need to figure out the area of a trapezoid for a household project? Even if you just want to sound smart, there is a simple formula that can be used every time you need to find the area of a trapezoid. Try the formula and see how good you are at geometry.

A trapezoid is a four-sided figure with one pair of parallel sides. Because a trapezoid can be dissected into a rectangle and two identical triangles, find it's area is easy.

You Will Need

* The dimensions of the trapezoid
* A calculator

Step 1: Sum the length of the two parallel sides

Add the lengths of the two parallel sides of the trapezoid.

Step 2: Multiply by the height

Find the height of the trapezoid. Using a calculator, multiply the sum of the lengths by the height.

Step 3: Divide by two

Divide the product by two. This is the area of the trapezoid.

For example, if the height of a trapezoid is 20 inches and two parallel sides of the trapezoid measure 13 and 15 inches, the area is given by = ½ × 20 × (13 + 15), or 280 square inches.

Step 4: Look for similar examples

Be on the lookout for other polygons whose areas can be determined more easily if the polygons are composed of simpler shapes.

The word trapezoid comes from the Greek word for table.