Whether buying, selling or building a house, the square footage of the house is one of the most important factors when determining the price or the cost of the house. Most houses have a main rectangular shape to them. From this main part of the house, small rectangular portions of the house may stick out. The more square footage a house has, the more the house will cost to buy or to build.
Divide the house into rectangles. For example, with an L-shaped house you would divide the main portion of the house from the part the branches off the house.
Measure the width of the rectangles from the front of the house to the back of the house. In the example, from the front of the house to the back measures 30 feet. For the smaller rectangle, where it connects to the house and back measures 15 feet.
Measure the length of the rectangles from one side of the house to the other side of the house. In the example, the main portion of the house measures 50 feet. For the small rectangle, the length from one side to the other side is 10 feet.
Multiply the width times the length of the each rectangle. In the example, for the main portion of the house, 30 feet times 50 feet equals 1,500 square feet. For the small portion of the house, 15 feet times 10 feet equals 150 square feet.
Add the area of the separate rectangles together to find the total square footage of the house. In the example, 1,500 square feet plus 150 square feet equals 1,650 square feet.