🎨 Paint Calculator
Figure out exactly how many gallons you need — accounts for doors, windows, coats, and surface type.
How to Use This Calculator
Enter your room's length, width, and ceiling height. Select how many coats you'll apply and choose your surface type (textured surfaces absorb more paint). The calculator subtracts standard door and window areas automatically and tells you exactly how many gallons to buy.
How Paint Coverage Works
Most interior paints cover 350–400 square feet per gallon on smooth surfaces. Textured walls, porous surfaces, and dark base coats all reduce coverage. The number of coats multiplies your total area requirement.
Subtract: (Doors × 20 sq ft) + (Windows × 15 sq ft)
Gallons = (Net Area × Coats) ÷ Coverage Rate
How Many Gallons for Common Rooms?
A standard 12×12 ft bedroom with 9 ft ceilings, 2 coats, 1 door, and 2 windows needs about 2.0 gallons for walls only, or 2.5 gallons including the ceiling. A large open-plan living area (20×16 ft) typically needs 3.5–4.5 gallons for walls plus ceiling.