How to Determine Square Footage in a House for Heating & Air Conditioning

The first step in determining what sort of heating or air conditioning system you need for your home is to figure the square footage or cubic footage of the living spaces within your home. Professional HVAC experts will ask this information at the beginning of the conversation, so it's handy to have a number to tell them. All you need is a measuring tape, a calculator, and a few simple formulas.

Step 1

Measure the length and width of each living space in your house that is heated or air conditioned. Do not include areas like garages or unfinished basements that typically do not receive heating or cooling.

Step 2

Multiply the length of each room with its width to derive the square footage of that room. For example, if a room is 15 feet long and 20 feet wide, the square footage of that room would be 300 square feet.

Step 3

Add the square footage of each room to arrive at the total square footage of the living spaces in your home.

Step 1

Measure the length, width and height of each living space within your home.

Step 2

Multiply the length, width, and height together to determine the cubic footage of each room. For example, if a room is 15 feet long, 20 feet wide, and 8 feet tall, then the total cubic footage for that room would be 2,400 cubic feet.

Step 3

Add the cubic footage of each living space within your house to determine the total cubic footage of all the living spaces.

Warning

• There are many factors to consider when selecting a heating or air conditioning system for your home other than the square footage or cubic footage of the living spaces. Professional contractors who do their job properly must also consider the type of insulation of the walls of the home, the heat loss from windows, the side of the house facing the sun, etc. Using the square footage or cubic footage of a home is a quick way to get a general idea of the size an HVAC system needs to be, but be wary of a contractor who doesn't consider the myriad other factors as well.