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How to Calculate Square Feet, Even If Your Home Is a Hexagon

By Margaret Heidenry | Jun 16, 2020


If you’re selling your home or looking to buy, one concept that’s crucial to understand is how to calculate square feet. Having to do a square footage calculation may be giving you panicked thoughts about being late to homeroom, but  there’s a huge difference between a home that’s 400 square feet (tiny) and one that’s 4,000 (McMansion), and not just in terms of how much space you’ve got to stretch your legs.

A home’s square footage is a crucial element in determining the price of a home you’re trying to buy or sell, how much you’ll pay in taxes if you live there, and what kinds of renovations are possible in your future. Plus, a home’s square footage can be surprisingly subjective.

Since most people don’t have a square foot calculator in their back pocket, here’s what you need to know to ace any square footage calculations that crop up in your future.

How to calculate square feet

You probably know how to calculate the square footage of a simple room without any funny shapes. Just break out your measuring tape—or a laser measure—to get its length and width. Multiply the width by the length and voila! You have the square footage. Say a room is 20 feet wide by 13 feet long, then 20 x 13 = 260 square feet.

How to calculate square feet
How to calculate square

How to calculate the square footage of an entire home

While measuring a single room is no big deal, people get kind of intimidated when it comes to calculating the square footage of an entire home. While homes can initially seem “daunting to measure, they’re just a collection of small boxes,” says Mario Mazzamuto of SF Bay Appraisal. Don’t sweat it if a room has an outcropping. Simply break that area down into a smaller box, and measure each box individually. Add up each box’s square footage to get the room’s total area. So if your living room, bedroom, bathroom, and hallway are  500, 400, 200, and 100 square feet respectively, that means the total is 500 + 400 + 200 + 100 = 1,200 square feet total.

Even complicated floor plans are just a series of rectangles you can add up.
Even complicated floor plans are just a series of rectangles you can add

If you have a round kitchen and a triangular rumpus room, fear not. Just check out vCalc’s handy calculator that will tell you how to calculate square feet no matter what polygon’s thrown your way. Once you choose a shape, the calculator will prompt you for the measurements needed to compute square footage.

Take the square foot calculation with a grain of salt

Now that you know how to calculate the square footage of a home, it’s time to bust your bubble with a big caveat: A square footage calculation is surprisingly subjective based on who’s doing the measuring. For instance, you measured the actual, livable square footage between the interior walls. But many architects use their own square foot calculation method, measuring the square footage from the exterior walls.

This explains why there are often discrepancies between your square foot calculations and those of a real estate agent, builder, or other sources.

“Many MLS services require a listing’s square footage to come from a specific source,” says Robin Kencel of Connecticut’s Stevens Kencel Group. So while you can make your own estimate, you may need to hire a certain professional to come up with a number that can be used on your listing; check with your Realtor or town’s building department to determine who that is.

As a general rule, “the square footage extends through the Sheetrock and framing to the exterior of the wall,” says Mazzamuto. Generally, to do the same for your measurements, add 6 inches per measurement, he says.