How to Count Square Footage of a Home

Adding up space and bedrooms before making a sale isn’t always as easy as it sounds.

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Could you rattle off the official square footage of a home if someone asked you? What about the actual number of bedrooms? If the answer is no, you're not alone. But if you're listing a home for sale or are about to make a home purchase, understanding the square footage of a home and what defines a bedroom is key.

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Where do you find the official square footage number? There are some standards to measuring the square footage of a home, however, "the problem is that it's specific to different regions," says Seattle real estate agent Sam DeBord of Coldwell Banker.

The first place to start, DeBord explains, is with the common property tax records, which contain the official recorded living space. If you’re selling your home, this is the figure that should be entered as the square footage amount on the property’s listing.

“That being said, there are a lot of properties that are finished beyond that,” DeBord says. But, rather than adding that to the official square footage number, the best thing to do is measure and describe the finished space in the marketing details.

“The most important thing is to list that property without any possibility of liability,” DeBord says. “If you list something that isn’t there, it’s a possible lawsuit down the road.” Not included in official square footage measurements:

  • Unfinished attics/basements, or attics/basements finished at a later date
  • Guest houses, guest suites, or anything you leave the main house to access
  • Garages, attached or otherwise
  • Exterior porches or attached decks
  • How to measure square footage:

    If you want to tackle measuring the square footage of your home yourself, there are a few different standards you can use. The most common technique for measuring a home is the American National Standards Institute (ANSI) calculation.

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    Measuring your home’s square footage using ANSI is done using the exterior walls. Start at a corner and work your way around the house. For example, if you have a perfectly rectangular home, you’ll measure the length of the home along one exterior side by the length of the other exterior side and multiply the two together.

    If your home is like most, it won’t be a perfect rectangle and you’ll have to deal with little areas that jut out or are angled. Measure those parts separately, calculate the area of each and then add that on the total square footage. Note that the ANSI's measurement guide does not apply to condos or multi-family housing.

    What defines a bedroom?

    Another confusing detail that shows up on a property’s listing regards the number of bedrooms. Like square footage, the standards to define a room as a bedroom vary from region to region.

    Officially, the number of bedrooms that are in the county tax records should be on the home’s listing. However, unlike square footage, there is a little more leeway, says DeBord. “There are technical rules, but as common practice it’s a little looser,” DeBord says. “A lot of people have finished basements with bedrooms—but most buyers would look at the room and agree that it’s a bedroom with a closet and a window.”

    One of the main things that constitutes a bedroom is an egress window—a window that could be used as a point of emergency escape or rescue. Real estate codes will vary, but most standards require the window must be operable from the inside without the use of a tool or keys, as well as have specific minimum and maximum window opening height and width as well as windowsill height and width. Bedrooms must also have a closet, but again, what defines a closet can vary in each region.

    Erika Riggs is a real estate writer for Zillow Blog, a resource for real estate and mortgage news. Twitter: @zillow.