**To calculate the area of an irregular shape, the shape needs to be divided into regular shapes that can have their area easily calculated; the area of the regular shapes can be added up to equal the total area of the irregular shape.** One way to calculate the area of a regular shape, namely a rectangle, is to multiply the length of the rectangle by its width. Different methods are used to calculate the areas of other regular shapes, such as circles, triangles and squares.

Most irregular shapes are a combination of two or more regular shapes. These shapes could be a result of a triangle and a rectangle or two rectangles. The shape should be divided into two or more separate parts that form regular shapes. It is important that the dimensions of the irregular shape should be the same size when they are divided into regular shapes. This is especially important in geometry problems that are on paper.

To find the exact dimensions of a regular shape in real life applications, the shape can simply be remeasured. It is important that the exact area of the shape be discovered before the shapes are added together. Remember to use the Pythagorean Theorem (a^{2} + b^{2} = c^{2}) to calculate the area of a triangle and simply use the length times width formula to calculate the area of a rectangle or square.