The Paint Coverage Formula Saves Money on Every Project

One gallon of paint covers approximately 350 to 400 square feet. That number is printed on every paint can and is wrong for most real situations. Porous surfaces textured walls and dark-to-light color changes all reduce coverage significantly. The formula Paint needed (gallons) = Total wall area (sq ft) / Coverage per gallon * Number of coats Total wall area for a rectangular room: function wallArea ( length , width , height , doors , windows ) { const perimeter = 2 * ( length + width ); const grossArea = perimeter * height ; const doorArea = doors * 21 ; // Standard door: 3x7 = 21 sq ft const windowArea = windows * 12 ; // Standard window: ~12 sq ft return grossArea - doorArea - windowArea ; } function gallonsNeeded ( area , coveragePerGallon = 350 , coats = 2 ) { return Math . ceil (( area * coats ) / coveragePerGallon ); } // 12x15 room, 8ft ceiling, 2 doors, 3 windows const area = wallArea ( 12 , 15 , 8 , 2 , 3 ); // 396 sq ft const gallons = gallonsNeeded ( area ); // 3 gallons Ad