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How to Measure Square Footage of a House

May 28, 2020 by Matt Frankel, CFP

The simple definition of the square footage of a house is the area of the living spaces contained within its walls. However, there's a lot more to the concept of square footage. Certain parts of a house are excluded from square footage calculations, and some that you might not think of are included. And others might have some gray area in regards to whether they should be included or not.

To be clear, there's no official laws that dictate how square footage is to be measured. For example, one real estate brokerage might include unfinished basements while others won't. With that in mind, the American National Standards Institute (ANSI) issues guidelines for calculating square footage that are widely regarded as the industry standard. So let's take a look at what is and is not included under these standards.

What is included in square footage of a house?

You'll see what I mean as we go through the included items, but the general rule is that spaces that share the same heating and AC as the main home, conform to the home's overall architectural standards, and are located above ground are included in the total square footage. For this reason, the terms square footage and finished square footage are often used interchangeably.

Here's a list of the parts of your house that are generally included in the square footage calculation using ANSI standards (Note: These standards apply specifically to houses, not condominiums or apartments.)

  • Most living spaces -- This is the most obvious one. Living rooms, dining rooms, bedrooms, kitchens, and other typical living spaces generally make up the bulk of your home's square footage.
  • Walls -- Here's the one way the ANSI guidelines may actually overestimate your usable living space. The standard practice calls for measuring square footage from your exterior walls, as opposed to measuring the actual interior dimensions of each room. This includes each wall as part of your square footage, although it obviously isn't usable space.
  • Stairways -- While they aren't necessarily livable space, stairways are part of the heated and cooled "main living area" of your home and are therefore calculated as part of your home's total square footage.
  • Closets -- Closets are certainly considered to be part of the main living area of the house, so most of your closet space is counted in your house's total square footage. On the other hand, closets in excluded areas, such as garages and basements, are typically not included.
  • Finished attic space -- To be included, an attic space must have at least seven feet of clearance and must be on the same HVAC system as the main living areas of the home. Plus, the finished space must have the same general quality and architectural standards as the rest of the home.
  • Enclosed porches -- Enclosed porches can be included in total square footage if and only if certain requirements are met. They must be enclosed on all four sides and have a roof and must be heated using the same system that also serves the main area of the house.

One thing to keep in mind is that the heating and air conditioning requirements only apply in markets where they're warranted. For example, when my wife and I bought a home in South Florida, it wasn't heated, but the living spaces were still included in the square footage.

It's also worth noting that there can be significant grey area with some of these items. For example, if an enclosed patio is tied into the home's HVAC system but is clearly not built to the same standards as the other living spaces, there can be a solid argument for or against including it in the home's square footage. In situations like this, it's a good idea to defer to the opinion of a professional appraiser.

What is not included in square footage of a house?

While it's not a set-in-stone requirement, ANSI standards generally exclude any spaces that aren't climate-controlled, any spaces that don't have four walls, any unfinished spaces, and any structures that aren't physically attached to the main home. This includes, but is not necessarily limited to:

  • Below-grade spaces -- This includes basements, even if they're finished. It's common for a real estate listing to include a note such as "500-square-foot finished basement not included in square footage of home," but under ANSI standards, it shouldn't be part of the official square footage calculation. If you're shopping for a home and see that it has a finished basement, it could be worth clarifying with the listing agent whether or not it is included in the listed total square footage.
  • Unfinished attics -- If an attic space isn't finished, it is excluded from square footage calculations. Even if it's finished, an attic space needs to have at least seven feet of clearance and must be on the same heating and/or air conditioning system as the other living areas of the house.
  • Porches (most) -- Any porch that isn't fully enclosed and heated isn't included in the total square footage of the house.
  • Garages -- Even if they're used for something other than storage or vehicle parking (such as a home gym), garages aren't included in square footage. The only way a garage is included in the total square footage of a house is if it's been converted into actual living space that meets the architectural standards of the rest of the home.
  • Detached living spaces -- This includes pool houses, accessory living units, sheds, and any other space that you need to leave the main living area of the home to access. For example, if you have a 1,000-square-foot guest apartment that is a completely separate building from the main house, it wouldn't be considered in the total square footage (but could certainly be mentioned in a real estate listing as additional living space).
  • Open spaces -- For example, if an area on your second floor is open to the living room below, the space without a floor isn't included in square footage calculations.

How to measure and calculate square footage of your house

Official square footage calculations are done by professionals. For example, an appraiser will likely calculate the square footage number that's recorded for your home for tax records, your local assessor's office, and other legal purposes.

Having said that, you can certainly do a square footage calculation yourself with a tape measure and a calculator. There are several methods you can use, but my preferred way is to measure the exterior of your home with a tape measure and multiply the calculated area by the number of floors to establish a base square footage. Then, measure and subtract the square footage of excluded areas.

As a simplified example, let's say that a single-story home is a 30-foot length by 50-foot width rectangle, which is 1,500 square feet of total area within the exterior walls. The only excluded space within this rectangular floor area is a one-car garage that measures 12 feet by 22 feet, or 264 square feet. Subtracting this from the total gives an official square footage of 1,236 sq. ft.

You could also find a square footage calculator online that could make the process much easier.

It's worth mentioning that in markets outside of the United States, you might see a home's living area listed in terms of square meters, so keep that in mind if you're looking abroad.

Why square footage is important in real estate

There are several factors that make up a home's value, but square footage is one of the most important. Many homes are valued based on their condition and square footage (price per square foot is an important concept in home pricing), so it's important to get an accurate measurement of a home you're planning to buy (or sell) to ensure that it's priced appropriately. After all, if a home is advertised as being 2,000 square feet but actually has 1,600 square feet, you could end up overpaying.

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