You save time and money by estimating the amount of paint to complete a job. Tools you need include a calculator and tape measure. For measuring vertical lines or long walls, enlist a helper.Continue Reading
Using a tape measure, take the measurements of each wall in feet. Measure both the width and height of each wall. Round the measurements up to the next foot in order to simplify the calculations and to allow for variance.
Calculate the area of each wall by multiplying the width and height of that wall. Once you calculate the area of each wall you intend to paint, add these together to determine the total square footage.
According to HowStuffWorks, it is acceptable to ignore the area of a single window, but multiple windows, sliding doors and fireplaces cover a significant amount of space. Unless you plan to paint them, calculate their area, and subtract that total from the square footage of the walls.
As of 2014, Lowe's estimates primer to cover 200 square feet and paint to cover 300 square feet. Use these numbers or those provided by the manufacturer on the product label. Divide the area you calculate by the coverage to determine the number of gallons the room requires. Keep in mind that smooth walls take less paint than textured or rough ones.