How to Measure the Square Footage of a House

The square footage of a property is a measurement of its living space calculated in square feet. One square foot is measured by marking out a square of space with each side measuring one foot. The total square footage of a property is the total number of one-foot squares of livable floor space. A property’s square footage can impact its appraisal value (which is a measure of a house’s market value) or how much you pay in property tax on your home.

There are no national standards in the US for measuring the square footage of a home, and the standards typically vary by state. However, the American National Standards Institute (ANSI) outlines certain standards to help professionals and homebuyers accurately measure the square footage of a home. For example, an appraiser following ANSI standards will only factor measurements of a house’s “finished” spaces accessible by heating or cooling systems and under a home’s ceiling into the home’s square footage calculation.

Square footage is important in real estate because it is the clearest representation of the total area of livable space in a homeowner's property. Here is an overview of the practical reasons that square footage is important.

• Home value: Square footage is one of the variables factored into setting the listing price or determining the fair market value of a house. If you order an appraisal for your new house to determine its fair market value, the appraiser will factor the square footage of this house to similarly-sized homes in the area.
• Securing a mortgage: Most mortgage lenders will require homebuyers to get a home appraisal before granting them a loan to protect the lender from promising more money than the house is worth. If your appraiser finds that a home is worth less than it is listed for—potentially because of a square footage discrepancy—the buyer may not get a loan for the house unless the listing price is adjusted to affect the appraisal value.
• Property taxes: Assessing your home and measuring the square footage can help gauge whether a homeowner is paying too little or too much in property taxes. Your property’s square footage directly impacts the assessed value of the house, which influences property taxes you’re required to pay.

Rooms that will typically be included in a home's square footage are any finished rooms that have a ceiling, walls, and a floor, such as living room, bathrooms, kitchens, bedrooms, and finished basements. Areas that are not typically included in the square footage of a home are garages, pool houses, unfinished basements, and attics.

Here is an overview of how to calculate the square footage of a house.

1. 1. Assemble your supplies. Bring a calculator, a tape or laser measure, a pen, and a notebook when you plan to measure the square footage of a space. You can draw out the floor plan with the notebook, measure the space with your tape measure, and add up your measurements with the calculator.
2. 2. Measure the separate areas of the house. Go through your house and measure the dimensions of each room one at a time. Measure a room’s length and width along the walls of each room in feet and note the metrics in your notebook.
3. 3. Calculate the square footage of each room. If you’re working with square or rectangular rooms, you can simply multiply the length of each room by its width to calculate the square footage. For irregular rooms, divide the space into geometric shapes, use the applicable formula, and add up the square footage. To measure the square footage of a triangular space, multiply its base by its height and divide that number by two. To calculate the square footage of a circular space, measure the circle's radius (the distance from the center point to the circle's edge), multiply that number by itself and then multiply the new number by pi (3.14).
4. 4. Add up the square footages of each room. Once you have the measurements of each room, add them all together to get your overall square footage. You can make the calculations yourself or use an online square footage calculator.

Here are few things to consider when preparing to measure the square footage or a property:

1. 1. Draw A Floor Plan. Make a rough sketch of your property's floor plan. This will give you a sense of how you’ll add your calculations for each room together. This is an especially important step if you’re measuring irregularly-sized rooms with a square footage that involve a little more calculation.
2. 2. Plan which rooms you will be measuring. When calculating square footage in any home, you should include the measurements of all the rooms in your house that are “finished,” enclosed by four walls, and are heated or cooled. You can measure spaces like garages, basements, or outdoor spaces for your own knowledge, but they should not be included in your square footage calculation.
   
3. 3. Take extra care with irregularly-shaped rooms. All you need to do to measure the square footage of square or rectangular areas is multiply length times width. However many rooms in a home will be more oddly shaped. To determine the square footage of irregular rooms, measure the length of each wall using a measuring tape and record the dimensions on your floor plan. Then divide the shape of your room into regular shapes like squares, triangles, or circles. Calculate the square footage of each separate shape and add them together to get the total square footage of the room.
4. 4. Remember the stairs. Include stairs in your home’s square footage calculation if you have them. Multiply the depth and width of one stair, then multiply that number with the number of stairs you have. Some appraisers will include the square footage of stairs twice, as they are considered a part of the floor plan of the floor from which they are descending and the floor to which they are descending. There are no standards governing whether you should include your stairs square footage twice.

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