How to Calculate Square Footage (And Why Most People Mess It Up) (2024)

If you’re looking to add a useful life skill to your metaphorical tool kit, consider learning how to calculate square footage. There are countless situations when calculating how many square feet are in a space comes in handy, from renting or buying a home to furnishing a place. The ability to calculate square footage also unlocks the door to lots of DIY projects.

To help teach you how to calculate square footage and how to use this knowledge to your advantage, we consulted two experts who work with this metric every single day: Greer Bronson, a Los Angeles–based real estate agent for AKG Christie’s International Real Estate, and Anne McDonald, a Minneapolis-based interior designer with a background in construction. Thanks to their insight, we’ve outlined everything you need to know.

What is square footage?

Square footage is the two-dimensional area of a space measured in square feet (which is sometimes denoted as sq. ft.). It’s the total area of every bit of floor in a room, home, or building. The term “usable square footage” is often used in real estate or interior design settings to describe the portion of the square footage that can actually be lived in, so it wouldn’t include an unfinished basem*nt or a technical closet.

How do I calculate square footage?

Bronson and McDonald agree that, in the simplest terms, the formula for calculating square footage is length (in feet) multiplied by width (in feet). But in reality, calculating square footage is more complicated than this basic formula, because many rooms are not a perfect rectangle. So the two experts helped us break down what you need to do, step by step.

Step 1: Measure the space.

Before you can calculate the square footage of a space, you need to determine its dimensions. Dimensions typically include length, width, and height, but you won’t be using height to calculate square footage. You can easily determine the length and width of your space with a tried-and-true old-school tape measure, which is how McDonald prefers it be done. Simply stretch the measuring tape from one side of the wall to the other and record each accurate measurement on a piece of paper.

Tape measure for home renovation and laminate flooring.Photo: m-gucci/Getty Images

For rectangular rooms, measuring the length and width is straightforward because there are only two measurements to take. When it comes to oddly-shaped rooms, we recommend dividing the space into smaller, rectangular sections and measuring the dimensions of each one. Measuring each niche and nook on its own will make it easier to calculate the square footage. If you’re calculating the square footage of an entire home, you should also measure closets, hallways, and staircases.

You can also use newer technology, like a laser measuring tool or a 3D camera, to determine the dimensions of your space. Appraisers often use such tools because they have the ability to calculate square footage for you too. “There are a lot of ways to measure digitally and I've seen that becoming more prevalent,” Bronson says. “The top two machines that I’ve seen are the Magpie and Matterport. Magpie is a laser that you can shoot at the wall and it'll calculate it all for you and create a floor plan. Matterport is a 3D camera that creates 3D house tours.”

Step 2: Apply the square footage formula.

Once you have measured your dimensions, you apply the formula, length x width, to determine how many square feet are in your space. If you’ve divided your space into smaller rectangles to account for an oddly shaped room, you apply this formula to the dimensions of each rectangle and then add all the products together to get the total square footage of the space.

The same formula works if you’re determining how many square inches, square yards, or square meters are in a space, assuming you’re measuring in those units of measurement. Alternatively, you can use an online square footage calculator, which does the math for you when you plug in your measurements.

Why should I know how to calculate square footage?

For renting, buying, or listing a home.

According to Bronson, knowing how to calculate square footage is crucial if you’re renting or buying a home because the listing is not always accurate. “On a lot of listings, there'll be a caveat like, ‘Agent does not confirm square footage. Please measure yourself.’ Or something along those lines so they can't be held liable if they’re a few square feet off,” she shares. Calculating the home’s square footage yourself will ensure it’s accurate and you’re getting what you pay for.

How to Calculate Square Footage (And Why Most People Mess It Up) (2024)


How do you solve square feet problems? ›

Multiply the length by the width and you'll have the square feet. Here's a basic formula you can follow: Length (in feet) x width (in feet) = area in sq. ft.

How do you calculate square footage per person? ›

Six square feet per person is a good rule of thumb for a standing crowd. If you are planning a co*cktail hour for 100 people who will all be standing, you will multiply 100 by 6 to determine you need a venue with 600 square feet of available and workable space for the event.

How is sq footage calculated? ›

Measure the length and width, in feet, of each room. Then, multiply the length by the width to calculate that room's square footage. For example: If a bedroom is 12 feet by 20 feet, it is 240 square feet (12 x 20 = 240). For each room, write the total square footage in the corresponding space on your sketch.

How to calculate square feet of an irregular shape? ›

Steps to find the area of an irregular shape
  1. Find all the unknown sides.
  2. Divide the irregular shape into squares and rectangles.
  3. Find the area of each individual squares and rectangles.
  4. Add all the individual areas to find the total area of the irregular shape. Total area = sum of all individual areas.
Sep 25, 2022

How to find square footage of 4 unequal sides? ›

Calculating area of land with 4 unequal sides would require you to first, sketch out the land using the dimensions provided. Then make an appropriate diagonal. Next, determine the areas of the two triangles that the diagonal creates. The size of the land is calculated by adding the areas of the two triangles.

What is the square foot method? ›

Square Foot Method – In appraisal, a method of estimating the replacement cost of a structure; it involves multiplying the cost per square foot of a recently built comparable structure by the number of square feet in the subject structure.

What is square foot estimating method? ›

What is a Square Foot Estimate? In simple terms, square foot estimates use an historical cost per unit, which is one square foot, and multiply that cost by the total number of square feet a building is expected to be.

How to calculate people per square footage? ›

The following steps outline how to calculate the People Per Square Foot. First, determine the total number of people. Next, determine the total square footage. Next, gather the formula from above = PSF = P / SF.

How do you calculate maximum occupancy? ›

How to Calculate Maximum Occupancy Load. The occupancy load is calculated by dividing the area of a room by its prescribed unit of area per person. Units of area per person for specific buildings can be found in the chart at the end of this article.

What is the 5 foot rule for square footage? ›

Did you know any portion of a wall below five feet in height is NOT considered to be living area? This is called the “5-foot rule” for calculating square footage, and the image below will help illustrate the rule.

How do contractors calculate square footage? ›

Measure the length and width of the building's walls. Multiply the length and width measurements to find square footage. Remember to multiply the square footage times the number of floors in the building if your facility has more than one floor.

How do you figure out how much per square foot? ›

Price per square foot is typically calculated by dividing the purchase or list price of a home by the overall total square footage of the home. For example, if a 1,000 square feet home is priced at $200,000, the price per square foot is $200. Price per square foot is a metric frequently used in real estate.

Does the upstairs count as square feet? ›

The second floor of a house would be calculated separately. If listed, you would share the square footage of a home per floor. Also, a finished attic space that is fit for living and has at least seven feet of clearance can be measured and included.

How to calculate square feet from length width and height formula? ›

To find the square footage, simply multiply the length and width. For example, if you want to find the square footage 20 feet × 20 feet floor, then multiply the dimension 20 x 20. Hence, the square footage of 20 feet × 20 feet floor is 400 square feet.

How many square feet is 12x12? ›

In the case of a 12x12 room, simply multiply 12 by 12, resulting in 144 square feet.


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