How to Find the Square Feet of a House

Draw a simple sketch of the house on a sheet of paper.

Measure the lengths of each outer wall with a tape measure and write your measurements in inches on your drawing. It's easier to multiply inches than a measurement containing feet and inches.

Divide the sketch into as few basic shapes as necessary. These shapes may include rectangles, square and triangles. If the house is one big rectangle or square, you won't need to do divide the sketch.

Find the area of each shape on your sketch. For rectangles and squares, multiply the width times the length of the shape. For triangles, multiply the base of the triangle times the height and divide by two.

Add the individual areas for each shape to find the total area of the house. Consider, for example, a home that is in two rectangles. One rectangle is 240 inches by 300 inches and the other is 240 inches by 360 inches. Multiply 240 times 300 to get 72,000 square inches for the area of the first rectangle. Multiply 240 times 360 to get 86,400 square inches for the second rectangle. Add the areas to get 158,400 square inches.

Divide the total area in square inches by 144 to determine square feet. In this example, you would divide 158,400 by 144 to get 1,100 square feet.