Knowing the perimeter, area, and volume of a room is very important to the designer and owner of a house. You should know the perimeter so you can decide how much room you have for the furniture. You need to know the volume and the area so you know how tall the ceiling is for the furniture. You may also want to know if the rooms aren't too big for the rest of the house. Lastly, you need to know the area for carpeting and flooring.