Buy Right

Homeowners and DIYers who paint occasionally lack the experience of a professional painter when estimating how much paint is needed for the job at hand.

Below are the types of questions you should consider and discuss with a paint store expert in order to get the best advice. These questions will help determine how much paint you need for your next project.

1. What is the square footage?
First, determine the area of the surface you want to paint, whether interior walls or the outside of a house. To calculate the area of the space yourself, measure the width and height of each wall. For each wall, multiply the width times the height to get the square footage. Add the square footage of each surface together to get the total.

Next, measure any windows, doors, or other breaks in the wall and subtract their square footage from your original calculation. Now you have the project area—the number of square feet you need to cover.

Next you will need the coverage rate of your paint, which you may be able to find on the container’s label. Most coverage rates are between 300–400 square feed per gallon. If you don’t know the coverage rate, use 350 to get a rough estimate.

To determine how much paint you will need, divide the total project area by the coverage rate. For example, the square footage of a 10’x10’ room with a ceiling height of 10 feet is about 400 square feet. If the coverage rate is 400 square feet per gallon, you need one gallon. If the coverage rate is 300 square feet per gallon, you’d need 1.33 gallons. After subtracting windows and doors, you’d probably only need one gallon for a typical 10’x10’ room. By the same method, a 20’x20’ room (with 10 feet ceilings), would probably require two gallons.

Many paint manufacturers and retailers provide automated paint calculators to help painters estimate the amount of paint they’ll need. View a list of online paint calculators.

2. Are you making a big color change?
The difference in color may have an impact on how much paint you will need. If the new paint color is similar to the old paint color, you will need fewer coats. However, if you change from a very dark color to a very light color, or from a very light to a very dark one, you may need three or even four coats. Some vibrant and dark colors—especially red, orange and purple—may take even more coats to get an even finish.

3. Is the surface textured?
Textured walls require more paint than smooth walls because they have more surface area. The greater the texture, the more paint is needed. You may need up to 50 percent more paint for rough textures.

4. Shiny or flat sheen?
As sheen decreases, coverage increases. Flat paints require less paint to cover, while semi-gloss and glossy paints require more paint. Generally, a job that takes two coats of flat paint typically takes three or more coats of semi-gloss or glossy paint.

5. Have you used primer?
New, unprimed drywall, plaster, and bare wood absorb more paint and require more coats than surfaces that have already been primed or painted with a base coat. Primers are usually less expensive than paint, and they are specially formulated to improve adhesion and fill porous surfaces.

Primer prevents the top coat from being absorbed and reduces the number of coats needed. Instead of primer, you can also use up paint leftover from a previous project by applying it as a base coat to even out the surface and color.

6. Do you need tinted primer?
Although primer is usually white, you can often ask your paint retailer to tint primer so that the color of the primer is closer to the final color. This will reduce the number of coats you’ll need. Consider using tinted primer for certain color changes. Some paint retailers will tint primer for you, but you should know that there are limitations to how much pigment can be added to primer. The color will not be the same as the final coat, but tinting primer will reduce the number of top coats you’ll need.

Tip: use gray primer when changing the wall color to red.

7. Looking for a place to buy recycled paint?
Most of the leftover latex-based paint collected by PaintCare is diverted to paint recyclers. If you’re looking for locations where to acquire recycled paint products for your painting project, view our list of stores that sell recycled paint.