How Much Spray Paint Do I Need?

People often ask for help determining the number of spray paint cans to buy for their project. Spray paint is difficult to gauge because the amount of spray paint used is highly variable and dependent on how it is applied and the amount of overspray you generate.

The number of spray paint cans needed will depend on the overall square footage of surface you need to cover, the amount of paint in each spray can, and the number of coats you need to apply.

The second point - the amount of spray paint per can, is easy to determine and the spray paint manufacturer will usually state estimated square footage of coverage per spray paint can. Hedrix custom spray paint typically covers about 20 Square Feet per 11oz aerosol spray paint can.

The third point - the number of coats needed, is also relatively straight forward. Normally you will achieve the best results with multiple thin coats, so plan on at least two coats. If you are using very bright spray paint colors, especially yellow paint colors or orange paint colors, then plan on 1-2 additional coats. Extremely bright colors could require 5 or more coats. Most neutral or deep colors will only require 2-3 coats to achieve an opaque coating of your paint color.

The first point - the overall square footage of the surface area you need to spray paint, can be figured out by using some geometry. The simplest way to figure out your square footage is to break your surface down into a bunch of rectangles. The area of a rectangle is length by width, so if measuring in feet, then multiple the length by the width and that is your square feet. Add up all the rectangles and you have your overall square feet. Divide that by 20 SqFt (or whatever the coverage of your spray paint is) and that gives you the number of spray cans.

If you are measuring the area in inches, then you can multiply the inches to get the total number of square inches, and then divide by 144 to convert this into the total number of square feet.

Keep in mind that some surfaces have more surface area than the length by width would indicate. For example, a textured surface has more surface area. A very textured area may have 2-3 times the surface area of a smooth area, so this needs to be factored in. Also, some surfaces like grids or shutters, have a lot of openings and while you don't need to paint the space, it may not be possible to spray around the space and you end up with overspray.

Multiply the number of cans you determine by the number of coats you may need to determine the overall number of spray paint cans you will need.

Lastly, it is usually a good idea to factor in a fudge-factor like 30% to account for waste, especially if you are having custom spray paint made. You want to make sure you have enough spray paint to complete your whole job to avoid any batch variation that may result from needing to order more.