It is important to correctly estimate the amount of paint needed for your project. Taking proper measurements of walls, openings, and ceilings will give you the square footage of your room or rooms. Take into account the condition of your walls, the color to be covered, and the surface you are painting before heading out to buy supplies.
Measure the Room
To estimate paint amounts, take out a measuring tape, pencil, and paper. If the project is to paint the walls and ceiling of an interior room, measure the widths of each wall and add them together. A sample room 10 feet by 12 feet would have two walls of 10 feet and two walls of 12 feet for a total of 44 feet.
Check the height of the wall. In the sample room, the wall height is 8 feet. Multiply 8 feet by the 44 feet for a total of 352 square feet.
For a flat ceiling, the square footage is determined by multiplying the room length by room width. This room would be 10 by 12 for 120 square feet of ceiling. If the ceiling is a tray shape or other design, add in the extra depth. If using the same paint for the walls and ceiling, add the ceiling measurements to the wall figures for a total of 472 square feet.
Window openings and doorways need to be measured and subtracted from the total paint calculations. The sample room has two windows that are 2 feet x 3 feet for a total of 12 square feet. It has one doorway that is 3 feet x 7 feet for 21 square feet. The 33 square feet of opening space must be subtracted from the 472 square feet of wall and ceiling space. The result is 439 square feet.
Painting Old or New Walls
A room with new drywall will need a coat of primer as well as a coat of paint. A previously painted room also may need a coat of primer.
Decide whether to prime before painting by checking the condition of the walls. If they are still in good condition with good paint, clean them and lightly sand off any gloss. Primer probably won’t be needed unless the new color is much lighter.
You should prime first if the paint on the walls is in poor shape or the project involves painting over wood. If you plan to use latex paint over an oil-based paint surface, you should also prime first.
Paint color choice will also be a factor. Painting with the same color latex paint won’t require a primer. If the project involves a new color, remember that it is more difficult to cover a darker color with a lighter color. If the new color is lighter, plan for two coats or use a primer.
Estimating Paint Needed
Coverage per gallon of paint varies depending on the texture and porosity of the surface. Experts suggest that one gallon of quality latex paint will cover approximately 400 square feet with one coat of paint.Surface texture also plays a role in coverage. When making calculations, it’s important to plan for extra paint needed for rougher or more absorbent surfaces.
Poor quality applicators also can affect paint coverage. Premium brushes and rollers are recommended for all painting projects. The correct tools provide the proper amount of paint to cover the surface. Check product labels. They may recommend specific applicators for best coverage.
Plan to buy more paint than the project calls for to save yourself trips to the store. Buying all the paint at once will also help insure color consistency. A bit of leftover paint—a quart or two—provides for those inevitable future touchups.
Credit: Renovate Your World