Whether we are budget-conscious, environmentally-conscious, or we just don’t like waste, no one wants to buy too much paint. At the same time, the last thing we want is to have to run out to the store for one more gallon, half-way through painting a wall. So, assuming you’re not a professional painting contractor with more ready-mix paint in your van, how do you calculate the right amount of paint to buy?

First, measure the height and width of each wall (and ceiling) you will be painting. Multiply the height and width to get the square footage for each wall, then add together the amount from each wall. So if you are painting two walls, and they are both 10 feet wide by 8 feet tall, that’s 80 square feet per wall, so a total of 160 square feet.

The next, and possibly more difficult, step is to determine how many coats of paint you will need (see below). There are many factors that influence this consideration, but in general, it is best to plan on two coats. However many coats you decide on, multiply your square footage by that number. So two coats at 160 square feet will be 320 square feet. Check the label on your paint, and see how many square feet a gallon will cover. For this sample 2-wall project, one gallon will probably do.

How do I know how many coats of paint to use?

If you are recoating a wall with the same color that was previously on it, then one coat will probably be sufficient, as long as the paint is still in good shape. One exception to this is in new homes where the current paint was applied during construction. Here in Valencia and throughout the greater Los Angeles area, many homes were originally painted using a very thin, cheap paint sometimes referred to as builder’s paint, or contractor-grade paint. If this paint is still the only coating on your walls, you may need two coats, even if you do not change colors.

If you are changing colors, it can become nearly impossible to predict how many coats you will need, because paint quality, previous color, new color, and application method can all impact this calculation. Professional house painters generally plan on at least two coats, even when covering a light color with a darker one. When covering a dark color with a light one, it will take many coats, and it is advisable to do your initial coats with a less expensive primer, tinted to a partial shade of your new color.
Finally, purchase higher-quality paints that have a greater “hide” factor. This is a measurable quality that is often mentioned in the paint manufacturer’s literature. You may well find that spending more money on the quality of paint saves money overall because you need to buy less of it.