How to Calculate Gallons of Paint for a Room
- 1
Measure the walls.tape measure image by Alison Bowden from Fotolia.com
Measure the walls using a tape measure. The goal is to find the surface area of the room by measuring the perimeter. Measure the length and width of each of the walls in inches and round those measurements to the nearest foot. Do not exclude any feet for the window measurements at this time. - 2
Add the wall measurements together.Mathematik image by bbroianigo from Fotolia.com
Measure the length and height of each wall. Multiply the length and height of each wall, and add those measurements together. For example, if all four walls measure 10 feet by 10 feet, the calculation would be (10 feet x 10 feet) x 4. The total wall area in the room equals 400 square feet. - 3
Measure the doors and windows.A shadow of a window cast on a wall in black and white image by David Smith from Fotolia.com
Measure the window and door areas. An average door measures approximately 21 square feet. On average, a medium-sized window measures approximately 15 square feet. For an exact calculation, measure the height and width of the windows and doors using a tape measure. - 4
Subtract the door and window measurements.la calculatrice image by Cyril PAPOT from Fotolia.com
Do the subtraction to get an accurate calculation. Subtract the area of the windows and doors from the total wall calculation. For example, if a room has one standard-sized door and two medium-sized windows, the calculation will be as follows: 21 square feet + (15 square feet x 2) = 51 square feet, so subtract 51 square feet from the original 400 square feet calculation: 400 - 51 = 349 square feet. - 5
Calculate total paint needed.yellow paint image by Jennifer Griner from Fotolia.com
Choose the number of gallons of paint. In most painting situations, 1 gallon of high-quality paint will cover 300 to 400 square feet depending upon the color and texture of the paint. The 300 to 400 square feet is for only one coat of paint. If the current wall color is light, one coat of paint might be enough. Flat paint tends to require a bit more paint to cover the walls when compared to its satin and gloss counterparts. If the current paint color is a medium or dark hue, two coats may be necessary. In the example, 1 gallon of paint would most likely be needed to put a single coat of paint on the walls in the room.
