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  • Writer's pictureCameron Maltby

How Do You Calculate Square Footage For Exterior Painting?

Updated: Jan 6, 2023

When you're painting an exterior surface, you have to determine the total square footage of the wall area that will be painted. For example, if you're painting an entire building, you can divide the total square footage by the number of windows and doors. Then, subtract the square footage of the walls that will not be painted. Therefore, you will have a total area of 2,108 square feet that you will need to cover.


The Shape of the Room

The shape of the room also matters. For example, a square room has six walls, while a rectangular room only has four. In addition, the shape will determine the number of windows and doors. You'll also have to multiply the length and width of the room to calculate the square footage of the exterior painting surface.


Once you have an idea of the overall square footage of your house, it's time to determine how much paint is needed. A good rule of thumb is to multiply the number of walls by the number of windows, assuming you're applying two coats of paint. Also, take into consideration that your house may have cathedral ceilings, which can cause sloping walls.

You'll need to subtract 15 square feet for each window and door, as well as the length of gutters. You'll need one gallon of trim paint for every six gallons of wall paint. For gutters, you can calculate linear feet as a standard measure of square footage.


Besides the square footage, you should also know the total area of your home. The walls of a home cover 51 square meters, so multiply the length by the width. You can deduct windows and doors from this to get a more accurate square footage for exterior painting. After you've done this, you can calculate the cost of painting your home.

Labor and Materials

The average cost of exterior paint depends on two factors: labor and materials. If you're doing the work yourself, you should know that one gallon of paint covers approximately 400 square feet of smooth surface area, while five gallons cover about 750 square feet of textured surface area. The paint cost per square foot can vary depending on the type of siding and the complexity of the job.


The height of your home can also affect the cost of the painting project. A home on the ground floor will be easier to paint than a home on two or three stories. You'll need a taller ladder and more paint, and higher-up homes are more likely to have obstacles such as fallen objects, tree branches, or power lines.

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