How to calculate the square footage of a house

Quick insights

• Square footage is a key metric used in property value assessments and many types of home improvement plans.
• You can begin to determine square footage by creating a rough sketch of your floor plan and working room-by-room with a measuring tape.
• Most rooms can be calculated by multiplying length and width, but more complex areas need to be broken up into smaller shapes and then measured.

Square footage is a standard measurement of a house’s total area. If you’re buying or selling a home, knowing how square footage is calculated can help you better assess or understand the value of a property. In this article, we’ll describe how to calculate the square footage of a house in a few steps.

Why square footage is important

Square footage is a significant factor in property value. Generally, a home with more square footage is more valuable than one with less, when other features are the same. This makes accurate measurements very important for buyers and sellers alike, as square footage can play a large role in determining price.

However, there are several other contexts in which square footage calculations are important:

• Legal and compliance:Certain areas have standards for buildings based around square footage, such as the minimum size requirements for rooms or living spaces. Square footage can also be referenced in zoning laws to designate allowable structure size on a specific lot.
• Property taxes:For homeowners, the square footage of your home may impact its assessed value and property taxes, as a result. Depending on the area, homes with more square footage can incur higher taxes.
• Home improvement:It’s common to calculate square footage for flooring installation, when adjusting the floor plan or before making other kinds of renovations.

The tools you’ll need to measure square footage

When measuring square footage, it's important to measure each room or area separately and account for any irregularities or alcoves to ensure accuracy. Most professionals now use digital floor-mapping programs to figure out the square feet available. You could try manually with measuring tape (or a laser measuring tool), graph paper, a calculator or pencil.

Here are some additional tools that may help you measure square footage:

• Measuring wheel:Also known as a surveyor's wheel, this tool is rolled along the ground to measure distance. It's useful for measuring larger areas, such as yards or outdoor spaces.
• Blueprints or Floor Plans: If available, blueprints or detailed floor plans can provide accurate square footage measurements. These documents are often used by architects and builders.
• Mobile apps:There are various smartphone apps available that can help measure square footage using your device's camera and sensors. These apps can be convenient for quick estimates.
• Online calculators: For irregularly shaped spaces, online square footage calculators can help you input various dimensions to get an accurate measurement.

Getting help from a friend or expert could be a bonus ingredient for success. A second set of hands can make it easier to take accurate measurements, especially in a large space.

How to determine square footage

To calculate the square footage of a house, you’ll need to work room by room, floor by floor.

Step 1: Create a rough sketch

Before you begin measuring, make a rough sketch of the layout of each floor. The drawing doesn’t need to be perfectly accurate in terms of dimensions (that’s what you’ll be measuring), but it’s important to include all nooks, corners and closets. You will use this sketch as your guide, filling in measurements for each length as you go.

Step 2: Measure one room at a time

Referring to your sketch, measure every length of wall in a consistent manner; and as the adage says, “measure twice.” Note your measurements in feet alongside the corresponding wall on your sketch. Don’t forget to include the dimensions for closets and hallways.

Step 3: Calculate square footage for each room

Rectangular or square rooms can be calculated most simply (length x width). Depending on the style of the home, you may also need to calculate the area of other, more irregularly shaped rooms. In these situations, you will need to find familiar shapes within the irregular space, calculate them as if they were separate rooms, and then add them together.

• For rectangular or square-shaped rooms: Multiply length by width to find square footage. For example, 10 feet (length) x 20 feet (width) = 200 square feet.
• For irregularly shaped rooms, such as an “L” shape:Divide the space into two or more rectangles, calculate them individually, and then add their sums together.
• For triangular rooms or those with a diagonal wall: Multiply the length of the longest edge by the “height” of the triangle and then divide it in half. Be sure to add any necessary rectangular measurements to your sum if the room is not a perfect triangle.
• For a rounded nook:For half-circle shapes, you will multiply 3.14 (π, also known as ”pi”) by the square root of the diameter, then divide by 2. If the room is not a perfect half-circle, be sure to add measurements for adjoining sections.

Step 4: Add your sums for the total

Working one floor at a time, add together the square footage totals for each room on that floor. If you have multiple floors, add together the sum of each floor to determine the total footage for the home.

What to leave out of your square footage calculation

When calculating a home’s square footage for real estate purposes, there are certain areas of the structure that should not be included in measurements. Areas that are typically excluded are non-livable areas of the property, which can vary slightly depending on the location, such as:

• Unfinished basements, attics and garages
• Spaces between walls, stairwells or elevator shafts
• Spaces that do not meet height restrictions, such as areas near vaulted ceilings
• Temporary structures like removable sheds or a seasonal poolside area

In conclusion

An accurate measurement of square footage is crucial to determining a fair property value. However, this detail can continue to be important long after the home is sold, playing a role in the owner’s property taxes and future renovations. When determining square footage, be sure to double-check your measurements, refer to local standards and consider seeking expert guidance for the most accurate total.