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How to calculate the square footage of a home

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When you buy a new place, thinking about how to measure the home’s square footage probably isn’t top of mind. And while it may seem like an inconsequential metric, it’s one of the most important factors that determine a property’s value. 

“That square footage number impacts your value, and if you mismeasure a property, it’s a domino effect. It’s going to throw the whole value off,” says Marlon Day, senior director of Quest Valuation and Advisors in Atlanta.

Why measure square footage?

There are plenty of reasons you might want to know how to calculate square feet of a house, whether you’re looking to sell a property, dispute a high tax assessment or renovate to add more space.

If you’re preparing to list your home, determining the property’s exact size is an important factor when deciding on an asking price. “For a home appraisal, we’re going to compare it to comparables or ‘comps,’” says Day. He will look for homes similar in size in the immediate area. When evaluating a home for sale, he also adjusts the value up or down for factors like building materials and condition.

However, knowing your home’s square footage can come in handy for other reasons as well. For instance, if you decide to finish a previously unused part of your house — say a basement or “bonus” attic space — you may need to provide the square footage to obtain a building permit.

Likewise, if your county or municipality assesses higher taxes than what you think you should owe, confirming the square footage can be a point in your favor to getting the property taxes reduced.

Why square footage matters 

In real estate deals that involve a mortgage, the lender will need to verify that the property is worth what the buyer has agreed to pay. “

It will all be revealed during the appraisal. You can run into pricing issues and property not appraising if the square footage is incorrect,” says Stamie Karakasidis, a Realtor with Rodeo Realty in Los Angeles. “Agents always encourage the buyer to verify square footage, but buyers need to do their due diligence,” she adds.

How to calculate square feet of a house 

When making plans for how to measure square footage of a house (or a condo or townhouse), start with a few simple supplies:

  • Note-taking supplies (paper, pencil)
  • Calculator
  • Measuring tape and/or laser measuring tool

If you live in a property that’s a perfect rectangle, simply measure the length and width and multiply the two numbers. For example, if your one-story house is 60 feet by 40 feet long, then your property is 2,400 square feet (60 x 40 = 2,400).

However, most properties have more complex floor plans, so it’s helpful to follow these simple steps to measure square footage.

  1. Draw out a rough sketch of your house, labeling all of the rooms you need to measure. Include hallways and other similar non-room spaces as their own “room” rectangles.
  2. Measure the length and width, in feet, of each room. Multiply the length by the width and write the total square footage of each room in the corresponding space on the home sketch.
    Example: If a bedroom is 12 feet by 20 feet, the total square footage is 240 square feet (12 x 20 = 240).
  3. Add the square footage of each room to determine your home’s total square footage.

If you live in a tract home, condo or townhome community, you may be able to get architectural drawings or master builder plans of your floorplan, which may already have your square footage calculated.

What to leave out 

A good rule of thumb for ensuring you’re taking proper measurements is to exclude space you can’t walk on or live in; it doesn’t count as “gross living area.”

“Someone might think, ‘If I get the measurement of my first floor and I have a two-story house I just multiply that by two,’” Day explains. However, if that first floor includes a two-story foyer, you can’t count the non-usable space. 

Basements and garages, even if they are finished, don’t generally count toward total square footage. Basements are typically excluded because they are built below grade, meaning below ground level. If your state does allow basements to be included in the total square footage of a home, though, you’ll likely need an ingress and egress, or a safe way to enter and exit the basement to the outside.

Finished attic spaces with some regulations including ceiling heights can count toward the total. If you are planning to sell your home, work with your agent to craft a listing that reflects the benefits of your property. 

“While I do not list (unpermitted space) as additional square footage, (in the listing) I do mention that there is additional space that can be utilized,” Karakasidis says. 

When in doubt, ask the pros 

If figuring out how to calculate square feet of a house feels overwhelming, it might be best to hire a professional appraiser. Depending on the size of the property, the fee might be as little as $100 up to several hundred dollars. While two different professional appraisers could evaluate the same home and come up with slightly different square footage figures, they aim for scientific accuracy.

“We’re always shooting for somewhere between 1 to 3 percent variance,” Day explains.

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Written by
Jennifer Bradley Franklin
Contributing writer
Jennifer Bradley Franklin is a multi-platform journalist and author, often covering finance, real estate and more.
Edited by
Deborah Kearns
Mortgage reporter