How to Calculate the Square Footage of Your Home

By: Philip Gvinter, DC Redfin Listing AgentSquare Footage

A house that sounds roomy and spacious online may actually have 800 of its square feet contained in a four-foot tall dirt-floor basement. What’s up with that? In Washington DC, my clients are often confused at the square footage discrepancy between what’s listed and what they see on tour, and my colleagues in other markets hear the same thing.

Why the conflicting information? Well, the American National Standards Institute (ANSI) guidelines on how to calculate a home’s square footage are considered the standard, but there are no official laws that govern this process. In addition, some Multiple Listing Services (MLS) report all finished and unfinished square footage as one number, adding to the confusion. Since the rules aren’t standard, some listing agents just post their best guess on a home’s square footage. As a result, buyers and their agents often have to investigate.

If you love a home, does it matter if the 2,000 square foot charmer turns out to be officially 1,600? Since square footage is used to determine a home’s market value, it can matter a lot. When it comes time for you to sell, 400 fewer feet can impact the price you’ll get, particularly in a buyer’s market.

What’s a buyer to do?

First off, start by referring to your city’s building department records. Many city and county records are now available online, which makes getting this info much easier than it used to be. Some updates – like unpermitted remodeling – may not be reflected in the records, but it will still provide a good baseline.

Then, familiarize yourself with basic ANSI guidelines for calculating square footage for single family homes. Practices can vary slightly from market to market, but these rules apply to most areas in the country:

  • Below grade spaces (basements, dens, etc.) do not usually count toward a home’s square footage. Even a finished basement can’t be counted toward a home’s Gross Living Area (GLA) but it can be noted separately in the listing.
  • The ANSI method specifies measuring from the exterior of the house, but wall width is not usually subtracted to account for actual living space.
  • Stairways and closet areas are included.
  • Finished attic square footage is included if an area has at least seven minimum feet of clearance.
  • Covered, enclosed porches can only be included if they are heated using the same system as the rest of the house.
  • Garages, pool houses, guest houses or any rooms that require you to leave the finished area of the main house to gain access are not counted.

Check it yourself.

Calculating Square FootageBuyers, consider checking advertised numbers by calculating square footage yourself; just multiply the length and width of all applicable rooms in the home. You’ll need a 100 foot tape measure, some graph paper, and a pencil. Pick a wall and begin making your way around the interior perimeter of the house in one direction, drawing lines accordingly on the graph paper (though ANSI guidelines specify measuring the exterior walls, measuring from the inside will give you a better idea of actual livable area). Assign a unit of measure to each square on the paper (a foot, for example) and measure to the nearest tenth of a foot. Then, go back over your floor plan, multiply the rectangular areas, and add them all up to get your final number. If your calculation includes area that is not permissible, don’t forget to subtract it out.

Note: Be aware that condominiums have fewer established rules and no ANSI guidelines. To start, you can visit your city’s building department and ask them to pull the home’s plans and permits for the property; the builders are required to include square footage for each unit. If that info is hard for you to get, you may want to hire an appraiser. If you’re a seller, it’s best to pay an appraiser to provide a square footage assessment so your listing is as accurate as possible. Finally, consult an agent. Agents usually see dozens of homes a week and have a pretty good spatial sense; they can often give you a ballpark idea of any home in question.

Finally, remember that while square footage is important to your home value, don’t focus on it at the expense of style or your emotional response to it. Do you like the design and floorplan? How about the location? Are there rooms you absolutely love? Numbers are important, but they are no substitute for the intangibles that make a house feel like a home.

Still have questions about square footage or have a story to share? Post a comment below!

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