How to Calculate a House's Square Footage

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Whether you’re buying or selling a house, every home listing and marketplace wants to know about a home’s square footage. The square footage of a house indicates how large a house is, and it’s an important number for sellers and buyers alike. There’s a big difference between 600 and 6,000 square feet, and that number will impact the bottom line.

Calculating the square footage of your home may sound like a daunting task, but it’s a crucial one. Before you panic and start asking questions like “Does the basement count as square footage?” read on for some help to calculate square footage, some useful square feet visualizers, and more explanation on what square footage means.

What is a square foot?

What even is a square foot? If you’ve forgotten most of your third grade math (like most of us, don’t worry), you might need a refresher.

One square foot is a square that’s 12 inches on each side. Imagine you have a tile floor, and each tile is exactly 12 inches by 12 inches square. Each of those tiles is a square foot. (That’s one of those square foot visualizers we mentioned before.) Chances are, your house isn’t made up of perfectly square tiles, so calculating exact square footage is a bit more complicated.

In any given space, multiply the length of the space by the width to get the total square footage. For instance, if your bathroom is a rectangle measuring six feet long by four feet wide, that’s a 24 square foot room.

Why is square feet an important measurement?

A home’s square footage might determine how much you’ll pay in taxes on your home and what kind of renovations you may do in the future. The most important factor of square footage, however, is determining the price of a home you’re trying to buy or sell. When you list a home for sale, the home’s square footage is an important number to help determine the list price. 

A real estate agent finds comparable properties, or properties of a similar size in the area that have sold recently to advise you on a fair offer price. A home appraiser uses a similar process of evaluating comparable properties, in addition to conducting an on-site review, to appraise the home’s true value.

Between you, the real estate agent, the appraiser, the architect, and the buyer, each entity may assess a home’s square footage differently. If you’re working with an agent and an appraiser to sell your home, it’s important to measure a home’s square footage accurately so you can reach a common agreement. An inaccurate square footage number could cause you to buy for too much or sell for too little, and could even hold up a sale entirely. For instance, if the appraiser doesn’t include the basement in square footage but your agent did, a buyer’s lender may not approve a mortgage for your agreed-upon sale price. You can contest a home appraisal as a buyer or seller, but it’s a time-consuming and expensive process. That’s why it’s important to accurately measure square footage and arrive at a number that everyone agrees upon.

Does a basement count as square footage?

We alluded to it, but one of the most common questions homeowners have is whether or not basements count as square footage. 

Square footage is also called “gross living area” (GLA), which is a good concept to consider when analyzing the basement question. If you can’t live in a space, you can’t count that square footage.

“Living area” means a room must meet certain criteria like height clearances, heating, and the presence of windows. GLA only includes above-grade square footage, so completely underground basements — finished or not — cannot count to a home’s overall square footage. 

To count towards a home’s square footage, a basement must be:

  • Finished to the same quality and standards as the rest of the house with walls, flooring, lighting, and other features that are similar to the main living areas.
  • Heated like the rest of the house. Space heaters (which are also a fire hazard) do not count.
  • At least partially above ground (requirements vary by state).

Those are the big qualifications. 

Then, nuances and variations to how rules apply impact whether a basement counts as square footage or not. Let’s look at some of the common scenarios in which basements are included to help you figure out if your basement counts.

To count as square footage, basements must have a legal entrance and exit so people can evacuate in the event of an emergency. That tends to mean that your basement is a walk-out basement with a door that leads directly outside, or a garden-level lot basement that doesn’t have a door that leads outside but does have windows that look out on the garden. Since the space is half above-grade with an exterior view, it may count as square footage. (Again, this is subject to different state requirements.)

How do you measure the square footage of your house?

On the surface, measuring the square footage of your house is simple. Just break out the measuring tape or a laser measure and measure each room’s length and width. Multiply the length by the width of each room, add them together, and you’ll have your square footage.

If your entire home is made up of quadrilateral (four-sided) rooms, you’re golden. Even if some rooms have an outcropping or closet, just break them into smaller boxes. A bedroom might be 10 feet by 10 feet and have an 8 foot by 3 foot closet, so add the 100 square feet of the room to the 24 square feet of the closet for the room’s total: 124 square feet. You can apply this to anywhere in the house as long as you’re working with four-sided rooms.

Of course, a space that isn’t quadrilateral becomes more difficult. Whether you have a round kitchen or a triangular living room, you can still calculate the square footage of any room with a little help. Square footage calculators like this one simplify the calculation process by providing square footage visualizers and tools to accommodate any shape of room.

If you don’t have a phone handy to use a special calculator, you’ll need to tap into that high school math. To measure the area of a triangular room, imagine you’re looking at it from above. Measure the height of the room, multiply it by the base, and then divide that number in half. 

For a circular room, measure the diameter (wall to wall) of the room and divide it in half. That’s the room’s radius. To calculate the room’s square footage, multiply the radius by itself (the radius squared), and then multiply the resulting number by 3.14 (pi).

How can you visualize square footage?

While you must eventually get a specific square footage number, people less enthusiastic about math may prefer using visuals to understand their home’s size. When you use visualizations, it helps you develop an approximation of the size of the rooms in your home and the house as a whole. That’s useful when you’re searching for your next home since you can imagine how the furniture and decor in your current home might fit in the rooms of your next one.

Some common home square foot visualizers include king-sized beds, two-car garages, or tennis courts.

  • A king-sized bed is 42 square feet.
  • A two-car garage is 400 square feet.
  • A tennis court is 2,800 square feet.

If you’re looking around the rooms of your house, ask yourself how many king-sized beds might fit in the room. Is the room larger than a two-car garage? Another useful method is to measure the length of your footstep and use that to image the square footage of a room. It’s not scientific, but using square foot visualizers is a fun way to conceptualize and contextualize square footage and compare your home to other places you frequent in your life.

Some other fun square foot visualization examples:

  • A basketball court is 4,700 square feet.
  • An Olympic swimming pool is 13,500 square feet.
  • A hockey rink is 17,000 square feet.
  • A football field is 57,000 square feet.

When you have a rough idea of square footage, you can use that estimate to look at similar sized spaces online and get inspiration for your current and future living spaces.

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