Paint Coverage Calculator

Buying the right amount of paint is a balancing act. Too little means a second trip to the store and risking a slightly different tint from a new batch. Too much means wasted money sitting in cans in the garage. This calculator gives you a reliable estimate based on your wall dimensions, the number of coats you plan to apply, and the area taken up by doors and windows. One gallon of paint covers approximately 350 square feet on smooth surfaces with a brush or roller. This is the industry standard coverage rate used by most major paint brands including Benjamin Moore, Sherwin-Williams, and Behr. Rough or textured surfaces like stucco, brick, or heavy knockdown texture absorb more paint and drop coverage to about 200 to 300 square feet per gallon. Almost every paint job requires two coats for proper coverage and durability. A single coat may look fine initially but will show wear faster, cover unevenly, and allow the old color to telegraph through. The main exceptions are touch-ups with the exact same color and going from white to white. If you are painting a dramatic color change like white over dark red, plan on a coat of primer plus two coats of finish paint. For a typical bedroom with four walls measuring 12x10 feet with 8-foot ceilings, the total wall area is about 352 square feet. Subtract roughly 40 square feet for a door and window, leaving 312 square feet. Two coats means 624 square feet of coverage needed, which is just under 2 gallons. Buy 2 gallons. Do not forget the ceiling if you are painting that too. Ceiling area is simply length times width of the room. Ceilings typically need flat or matte finish paint which hides imperfections better. Walls usually get eggshell or satin finish for easier cleaning. Trim and doors use semi-gloss for durability and easy wipe-down.