Square footage is a measurement of area, and area is the measurement of any two-dimensional space contained within a set of lines. Think of it in the sense of a dance floor. Take a moment to imagine a dance floor that is 20 feet by 20 feet (6.09 meters by 6.09 meters). How do we express the area that it takes up? This one is easy, because the dance floor is a square. We simply multiply the width of the floor by the length of the floor, 20 feet times 20 feet equals 400 square feet. Therefore, the total area of the dance floor is 400 square feet (37.2 square meters). The equation is the same for a rectangle [source: MCWDN].

Area of a square or rectangle = Width x Length

It's important to keep in mind that a square foot doesn't necessarily have to be shaped like a square. The dance floor above could be shaped like a triangle and cover the same amount of area. If you were asked to determine the area of a triangle or a circle, the equation would be different, but the concept is the same. Plug in the right numbers and you'll get the right answer. Both equations are listed below.

Area of a triangle = ½ (Base x Height)

Area of a circle = 3.14 x radius^{2}

So we've established that the square in square feet doesn't refer to shape. All measurements of area are expressed in square units -- the standard foot just happens to be the unit used in U.S. real estate.

Read on to find out how to calculate the square footage of a house.