How to Measure the Square Footage of a House

How to calculate square footage of a room

Calculating the square footage of a room requires some very basic geometry. You’ll need to calculate the area of each room in your house — be sure to only include rooms that count toward your gross living area (GLA) — and add them together.

Before you start measuring, make sure you have the following tools on hand:

  • Tape/Laser measure
  • Graph paper
  • Pencil
  • Calculator

Draw a rough sketch of the floor plan for your house. Don’t worry about being accurate. You just need something to help you keep track of all the rooms you’re measuring.

👷 Pro tip! Don’t forget to include closets, pantries, and other small rooms in your plan. They can be easily overlooked, but they usually count toward your total square footage.

Next, start measuring! You’ll use different formulas depending on whether a room is a:

Chances are most if not all of the rooms in your house are rectangular. That’s good news, since the area of a rectangle is easy to calculate. All you do is multiply length by width. Or, to put it another way, multiply the length of the longest wall by the length of the shortest wall.

As your geometry teacher would write it:

A = L x W

Where A equals area in square feet, L equals length in feet and W equals width in feet.

Let’s take the following room as an example:

First we measure the length of the longest wall, w

First we measure the length of the longest wall, which is 20 feet by the length of the shortest wall, which is 15 feet.

We then multiply 20 by 15 and get 300. So, the area for this room is 300 sq/ft.

💁 What about alcoves and oddly shaped rooms? If you have a room with alcoves, fear not! Simply measure the area of the alcove using the same equation as above (assuming it’s a square or rectangle). Then, add the total to the area of the main room. If you have an oddly shaped room, such as an L-shape, split it into square or rectangular sections and treat them as two separate areas. Not every space is linear, but you can still determine the square footage of an area by dividing it into shapes and calculating each shape's individual area.

Triangular rooms may sound strange, but they do happen. You may for example, have a corner of a room that has been turned into a closet or pantry.

Fortunately, finding the area of a triangle is very easy. Multiply the length of one side by the height of the triangle and then divide the answer by two.

That might sound tricky, but it’s actually really simple. The following example will show why.

The first step is to measure one side of the trian

The first step is to measure one side of the triangle. This side will be your base. In the above image, the base is four feet.

We then imagine a perpendicular line traveling from the base to the opposite corner of the triangle. In the above picture, this is the dotted line, which is your base height. In our example, the base height is 3.5 feet

Then we multiply the base by the base height, which gives us 14.

Finally, we divide our answer by two. For our tiny room above, the final answer is 7 square feet.

📐 Calculating the area of a right triangle Calculating the area of a right triangle — which is a triangle where one corner is 90 degrees — is even easier. Just multiply the two sides that are joined together at the 90 degree corner and then divide the answer by two!

Calculating the square footage of a circular room is a bit more complicated, but it’s still quite easy. If your room is a perfect circle, you can calculate the area by multiplying pi (which is approximately 3.14) by the radius of the room squared.

Still confused? Let’s take an actual example and you’ll see how simple it is!

The first thing you need to do is find the radius

The first thing you need to do is find the radius of the room. To do that, simply measure from the center of the room to the wall. If you can’t find the center, measure the diameter of the room (i.e., the furthest distance between the walls) and divide it by two.

In our above example, the radius is five meters. So, we square the five — which simply means multiplying five by itself — and get 25.

Then we multiply 25 by 3.14 (again, that’s the rounded figure for pi).

The answer is 78.5. Since we round to the nearest whole foot when calculating the area of a house, we’ll say that the area of the room is 79 sq/ft.

Do insurance agents calculate square footage the same way?

You may also wonder how square footage is calculated or used within a homeowner’s insurance policy. We reached out to Scott Teece, managing producer at Edina Realty Insurance, to get the details.

When creating an insurance quote for a client, Edina Realty Insurance typically pulls from the MLS listing to ensure they are assessing the same square footage as indicated in the property records. But while homebuyers care mostly about finished and unfinished square footage, insurance agents take special notice of a different breakout — above ground square footage and below ground square footage.

“When offering coverage to a homeowner, we calculate the total replacement cost of the property,” explains Teece. “Both above ground and below ground square footage are factored into that calculation, but the cost to replace the above ground square footage is typically somewhat higher. That’s because, for example, if a catastrophic event like a tornado or fire should occur, you’d likely have to reframe the first floor and above, but not the basement.”

In other words, a 2,000-square foot house without a basement would likely have a higher replacement cost than a home with 1,000 square feet of above-ground living space and a basement sized at 1,000 finished square feet.

When Teece and the Edina Realty Insurance team draw up a homeowner’s insurance quote, they rely on the MLS’ breakout of above ground square footage and below ground square footage to make their assessment.

Have additional questions? Contact the team at Edina Realty Insurance for more information or a personalized quote.


Is a porch included in a home’s square footage?

To be counted as finished square footage, a porch must be four-season. A four-season porch is much like any other room in the house, except that it provides clear views of the outdoors all year through a variety of windows. Four-season porches must have permanent heat sources to be included in a home’s finished square footage.

If a porch isn’t heated or only has screens (with no glass windows), then it is not part of the finished square footage count.

Does a basement count as square footage?

As a general rule of thumb, basements usually do not count towards the square footage of a house. For a basement to increase a home’s square footage, it must meet certain criteria to be considered livable space, and such criteria can vary between states. Your local county assessor’s office determines whether appraisers can choose what is considered square footage towards a home’s Gross Living Area. Below we highlight some of the most common criteria a basement may have to meet to be included in your home’s total square footage.

  • A portion of the basement is above-ground – Basements that are 100% below ground usually do not count towards the square footage of a house.
  • The basement is finished – Flooring, walls, lighting, and other features must be similar to the main living areas of a house.
  • The basement is heated and conditioned – You cannot use a space heater to heat up a basement. 
  • The basement has legal ingress or egress – To account for safety, a legal escape point is necessary in case a fire breaks out. This could be an egress window or walkout door that leads to the outside.

Get in touch with a real estate agent or appraiser to best understand if your basement can be counted towards the square footage of your home.

What Is Included In The Square Footage?

In measuring the square footage of a house, it is crucial to know what can and can’t be included in the calculations. Not every foot of your home enclosed by walls will count towards total square footage. Instead, you are trying to determine the gross living area — or the livable parts of your home. Keep reading to learn more about the specifications for measuring square footage:

Height Requirements

There is one measurement far too many inexperienced “appraisers” forget about: ceiling height. That’s not to say you measure the area as a three-dimensional space, but rather that the ceiling is one of the criteria I already alluded to. You see, for an area’s square footage to count in the home’s overall square footage, the ceiling above it must be a certain height. According to ANSI’s American National Standard For Single-Family Residential Buildings, finished areas must have a ceiling height of at least seven feet, “except under beams, ducts, and other obstructions where the height maybe six feet and four inches.” On the other hand, Angled ceilings must rest at the previously discussed seven feet for at least half of the room’s total floor area. If the ceiling is at least seven feet for at least half of the room’s floor area, total square foot calculations should include every area where the ceiling is at least five feet tall.

Garages, Protrusions, and Unfinished Areas

No matter how much you may wish your garage was included in the total square footage of your house, it’s not. I repeat, garages are not included in the total square footage of a property, even if they are finished — that’s because they are not the same level as the home itself. Similarly, chimneys and window areas are not included in a home’s square footage; not only are they not finished, but they are not on the same level.

Finished Home Connections

If you have a finished area connected to the house by a finished hallway or stairway, the subsequent area may be included in the home’s total square footage. However, finished areas connected in any other way (like by an unfinished hallway or staircase, for instance) won’t be included in the home’s total square footage.

Basements & Attics

Basements do not typically count towards a home’s gross living area regardless of whether they are finished. Since they are below the rest of the home, basements can’t be included in the total square footage. That said, homeowners may note the size of a finished basement in a respective listing elsewhere. On the other hand, attics may be counted in a home’s total square footage if they are finished and meet the height requirements stated above.

Covered, Enclosed Porches

Covered, enclosed porches may be included in a home’s gross living area if they are finished, and they are heated using the same system as the rest of the house.

How is square footage measured? 

To calculate square feet you multiple the room’s length by its width. For example, a space that measures 10 feet by 10 feet totals out to 100 square feet.

Length x Width = Area Ex. 10 ft. x 10 ft. = 100 square feet

While this may sound simple enough, it can be complicated measuring the square footage of a house due to odd-shaped spaces and living space gray areas.

“Here in North Carolina, square footage is calculated to the outer edge of the dwelling. So to properly calculate the square footage, an owner would need to calculate the area by multiplying the length by width, and including the wall thicknesses in their measurements,” explains Matt Harmon a North Carolina-based, state-certified property appraiser.

“For example, if a square house measured 20-foot by 20-foot when measuring to the interior walls, and the walls were 0.4-foot thick, then to calculate the area, you’d need to multiply 20.8 by 20.8 to find the exact square footage.”

However, if you’re selling a condo in a multi-family unit — meaning that you only own the interior space, not the exterior building — you would only measure square footage from interior wall to interior wall.

Finished basements and attics do not add to the primary square footage

The square footage of a finished basement that is below grade (underground) adds less value than the square footage of above grade living space.

So if your home is 2,000 square feet, and you have an additional 1,000 square-foot finished basement, you cannot claim to have a 3,000 square-foot home if your local area values basement spaces at a lower dollar amount than the rest of the house.

In this instance, you would list your home at 2,000 square feet and then include the additional 1,000 square feet of living space in your finished basement in the listing notes.

The same is true of finished attic spaces. If the space has sloping roofs, inadequate windows, and forms of egress, then the area may not count towards your overall square footage.

To determine if your space makes the cut, consult an appraiser or an experienced real estate agent.

Source: (Point3D Commercial Imaging Ltd. / Unsplas
Source: (Point3D Commercial Imaging Ltd. / Unsplash)

4 Tips for Determining Square Footage

Here are few things to consider when preparing to measure the square footage or a property:

  1. 1. Draw A Floor Plan. Make a rough sketch of your property's floor plan. This will give you a sense of how you’ll add your calculations for each room together. This is an especially important step if you’re measuring irregularly-sized rooms with a square footage that involve a little more calculation.
  2. 2. Plan which rooms you will be measuring. When calculating square footage in any home, you should include the measurements of all the rooms in your house that are “finished,” enclosed by four walls, and are heated or cooled. You can measure spaces like garages, basements, or outdoor spaces for your own knowledge, but they should not be included in your square footage calculation.
  3. 3. Take extra care with irregularly-shaped rooms. All you need to do to measure the square footage of square or rectangular areas is multiply length times width. However many rooms in a home will be more oddly shaped. To determine the square footage of irregular rooms, measure the length of each wall using a measuring tape and record the dimensions on your floor plan. Then divide the shape of your room into regular shapes like squares, triangles, or circles. Calculate the square footage of each separate shape and add them together to get the total square footage of the room.
  4. 4. Remember the stairs. Include stairs in your home’s square footage calculation if you have them. Multiply the depth and width of one stair, then multiply that number with the number of stairs you have. Some appraisers will include the square footage of stairs twice, as they are considered a part of the floor plan of the floor from which they are descending and the floor to which they are descending. There are no standards governing whether you should include your stairs square footage twice.

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