How to get square feet of a wall

Purchasing enough paint for an entire room all in one batch helps ensure the color stays consistent, since the paint can be mixed all at once. On the other hand, if you buy only 1 gallon of custom-tinted paint and then go back later for more of the same color, you may be in for an unpleasant surprise when the paint doesn't quite match. Calculating the room's square footage ahead of time helps ensure you buy enough paint for the job the first time.

Measuring Square Footage

For any room, a wall square footage calculator, which can be found on a paint company website, makes it really easy to estimate the square footage of the walls. If calculating the square footage yourself, start by measuring the length of one wall. The opposite wall is most likely the same size, but if not, measure that one too.

Measure the length of one of the other two walls, or both, if they are significantly different. Finally, measure the distance from floor to ceiling. Even if the room has baseboards that you do not wish to paint, don't omit those from the calculation, because it's nice to have a little paint left over for touch-ups.

Plug these numbers in to the square footage calculator, or multiply the length of each wall, either in inches or rounding up to the nearest foot, by the height. The result is the square footage of that wall. Add together the square footage of each wall to find out the square footage of all the walls.

Window and Door Concerns

Since all rooms have at least one door and most have windows, feel free to subtract the square footage of these elements from your wall calculations. Either measure the square footage of each window and door individually, or estimate these numbers. The typical door is 21 square feet, while the average window is 15 square feet. Subtract the total square footage of windows and doors from the wall square footage to determine the total square footage of wall space requiring paint.

The typical online paint calculator square feet measurements include estimates, not exact measurements, of window and door sizes, as well.

Paint Calculation Formula

Now that you've determined the room's square footage, it's a bit easier to figure out how much paint to buy. One gallon of paint typically covers 400 square feet with one coat of paint. Many wall-painting jobs require at least two coats of paint, especially if the new wall color is significantly different from the old. The paint calculation formula is as easy as determining how many gallons of paint are needed for one coat on the walls in the room. One gallon of paint is often enough for a tiny space such as a half-bath, while 2 gallons is enough to paint another coat or to paint a medium-sized room.

If the room has 500 square feet of wall space, for instance, buy 2 gallons of paint to apply one coat to the walls, which will leave enough left over for almost a full second coat.

Factors Affecting Paint Totals

If the room is already white and you're just painting it again with nearly the exact same color, you may be able to get by with just one coat on each wall. If the new or old color is dark or bright, expect at least two or three coats per wall. If the walls are porous, as some stucco and plaster walls are, expect to apply at least two coats.

How to Measure the Area

To get started with measuring your area, you will need your tape measure (or digital measurer) and somewhere to record your notes. Feel free to use a pen and paper or the notepad in your phone to log your measurements.

Before measuring, clear away any furniture that would limit your ability to measure your room. A clear space between the opposite walls you’re measuring is required so that there are no objects in the way of your measuring tape. To measure the distance between opposite walls, secure one end of your tape measure to the floor against one wall using tape or the assistance of a partner, keep the measuring tape straight until it reaches the next wall. Record the measurement reflected on the measuring tape once it touches the opposing wall in your phone or on paper. Repeat this process to find the distance between the other two opposing walls to determine the room’s length and width.

If you are working with a digital measurer, the numbers you’ll need to record will be reflected on the device’s screen rather than the tape itself.
When using a tape measure, ensure the tape is kept straight. The tape should not be bent, nor should you measure around objects.

How to Calculate Square Footage

Once you’ve got the measurements for the distances between your two sets of walls, you know the length and width of your room. These dimensions are essential to calculate the square footage of your room.
To find the area of a rectangle or the square footage of your room, we will multiply the length by the width.
Length x Width = Square Footage
For example, say you’ve measured the distance between the walls of your room and discovered that there are 12 feet between the first two walls and 12 feet between the second two walls. In this case, your length and width would be 12 feet by 12 feet. You will multiply the 12 foot width by the 12 foot length to find the square footage of your room which is 144 square feet.

12 ft x 12 ft = 144 ft²

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Converting Inches to Feet

When room measurements are not a whole foot, how do you convert inches to feet? Since there are 12 inches in 1 foot, to convert inches to feet, simply divide the inches by 12.
For example, if your room measured at 10 feet 3 inches wide, you could convert that measurement to feet by dividing 3 inches by 12 which is .25, and adding it to the 10 feet.
3 inches / 12 = .25 feet
Therefore, the width of the room is 10.25 feet.

If the room you’re measuring is a square or rectangle, feel free to skip over the irregular shapes section to the square footage calculator.

How to Calculate Square Feet of Irregular Shaped Rooms

It is common for rooms to not be a perfect rectangle or square. In these cases, we will include additional steps to calculate the square footage of irregular shaped rooms. The additional step will use the same square footage formula we’ve already reviewed and add the multiplied length and width of the irregular shape.

Length x Width = Square Footage of Main Section

Length x Width = Square Footage of Small Section

Square Footage of Main Section + Square Footage of Small Section
= Total Square Footage of the Irregular Room

For example, the main section of a room measures out to 12 feet by 12 feet, and an additional space of the room measures out to 5 feet by 7 feet. To find the square footage of this irregular-shaped room, we will find the square footage of the main section and the small section and then add them together.

Square Footage of Main Section
12 ft x 12 ft = 144 ft2

Square Footage of Small Section
5 ft x 7 ft = 35 ft2

Total Square Footage of the Irregular Room
144 ft2 + 35 ft2 = 179 ft2

Examples for Calculating Square Footage

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How many square feet is a 20x20 room?

The square footage of a room 20 feet wide and 20 feet long is 400 square feet. The square footage is found by multiplying the width (20 ft) by the length (20 ft).

L x W = Sq. Ft

20 ft x 20 ft = 400 sq. ft

How many square feet is a 15x15 room?

The square footage of a room 15 feet wide and 15 feet long is 225 square feet. The square footage is calculated by multiplying the width (15 ft) by the length (15 ft).

L x W = Sq. Ft

15 ft x 15ft = 225 sq. ft

How many square feet is a 13x13 room?

The square footage of a room 13 feet wide and 13 feet long is 169 square feet. The square footage is found by multiplying the width (13 ft) by the length (13 ft).

Length x Width = Square Feet

13 ft x 13 ft = 169 sq. ft

How many square feet is a 12x12 room?

The square footage of a room 12 feet wide by 12 feet long is 144 square feet. Find the square footage by multiplying the width (12 ft) by the length (12 ft).

L x W = Sq. Ft

12 ft x 12 ft = 144 sq. ft

How many square feet is a 10x10 room?

The square footage of a room 10 feet wide by 10 feet long is 100 square feet. Find the square footage by multiplying the width (10 ft) by the length (10 ft).

L x W = Sq. Ft

10 ft x 10 ft = 100 sq. ft

How many square feet are in a 12x16 room?

The square footage of a room 12 feet wide and 16 feet long is 192 square feet. Find the square footage by multiplying the width (12 ft) by the length (16 ft).

L x W = Sq. Ft

12 ft x 16 ft = 192 sq. ft

Square Footage Calculator

Once you have the dimensions of your room recorded, use the calculator below to find the square footage of your room. Use the fields labeled length and width to input your measurements and click ‘Calculate’.

For non-rectangle, irregularly shaped rooms press the ‘Add Space’ button to have the option to add additional lengths and widths to your square footage calculation.

The next step will help you determine how much flooring material you’ll need to purchase for your flooring project.

Floor Width
Floor Height

Example:12.25 (12' 3")

Total (of all rooms)

How Much Flooring Do I Need?

Once you have found the length and width of your room and calculated its square footage, you’ll need to adjust for the probable waste. This is to compensate for mistakes and other unforeseeable accidents as you complete your project. The amount of excess material you’ll need in addition to the room’s square footage will depend on your project’s material and your level of installation experience. CALI recommends an additional 5% of material for vinyl flooring projects and an additional 10% for engineered or solid hardwood flooring projects. That said, you may be wondering, “how much flooring do I need?”.

Let’s continue with the examples above. If we have determined that the square footage of a room is 179 ft2, then we need to add a percentage of excess material in order to find the total material to order. The process looks like this:

Square Footage of Room x Percent Excess Material = Excess Material Needed

Excess Material Needed + Square Footage of Room = Total Square Footage to Order

The total amount of material we will need for a vinyl flooring project in a 179 ft2 room is 188 ft2 (rounded to the nearest square foot). To find this, we’ll convert 5% to a decimal and use the formula introduced above.

Amount of Excess Material Needed
179 ft2 * .05 = 8.95 ft2

Total Materials to Order
179 ft2 + 8.95 ft2 = 187.95 ft2

To find the total amount of flooring material we’ll need, use the calculator below. Enter your room’s square footage and the percentage of extra material you anticipate needing and click ‘Calculate’.

Total Area of Rooms

Percentage Over (ex: 10%)

Total Needed

Rounded up to the nearest foot

If you’re still unsure about the amount of excess material you may need, you can call the flooring experts at CALI at 1(888) 788-2254 for advice.

Square Footage Calculations FAQ

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How do you calculate the square footage of a room?

To find the square feet of a room, multiply the length of the room by the width of the room. The length and width can be found by measuring the distance between the two sets of walls opposite each other in your room.
Length x Width = Square Footage of a Room

Example:

Room Length= 6 ft

Room Width= 3ft

6 ft x 3ft = 18 Ft2

How do you calculate square feet from inches?

To calculate the square footage of a space based on square inches, divide the square inches value by 144.
Square Inches of a Room / 144 = Square Footage of the Room.

Example:

Room = 2,592 In2

2,592 In2 / 144 = 18 Ft2

How do you calculate the square footage of a circular room?

To find the square footage of a circular room, start by measuring the diameter of the space. The diameter can be found by measuring the distance from one wall, through the center point of the room, to the opposite wall of the space. Once you have the diameter, divide it by 2, multiply it by itself, and then multiply that by 3.14 to get the square footage.
For example, if your circular room is 20 feet across (when measured through the center of the space), then the room is 314 ft2.

(Diameter / 2) x (Diameter / 2) x 3.14 = Square Footage

20 ft / 2 = 10

10 x 10 = 100

100 X 3.14 = 314 ft2

How do you calculate the square footage of a triangular room?

To find the square footage of a triangular room, begin by measuring the length of 1 wall. Then measure the distance from that wall to the corner, opposite the wall whose length you measured. Once you have the wall length and the corner to wall length, multiply those values then divide by 2.

Length of 1 Wall x Distance from Measured Wall to Opposite Corner / 2 = Square Footage

For example, if the wall you measure was 15 feet long, and the distance from that wall to its opposite corner was 20 ft, the square footage of the triangular room would be.

15 ft x 20ft / 2 = 150 ft2

What’s Next?

Throughout this guide we’ve used the length x width formula to calculate the square footage of a room for flooring, we have discussed irregularly shaped rooms (including circular and triangular spaces), and determined how much extra material you’ll need on top of your room’s square footage to make up for mistakes and plank adjustments.

So, now that you know the total square footage of material you’ll want to order for your project, what’s next? If you haven’t selected a material for your room yet, explore our guide below to learn about choosing a material that meets your needs.

How many square feet is a 10x10 wall?

How do you calculate the area of a wall?

How many square feet is a 8x10 wall?

How many square feet of wall is in is a 12x12 room?