Paint Calculator

Measure total wall area (2 x (length + width) x height), subtract doors (~21 sq ft each) and windows (~15 sq ft each). Divide by coverage (typically 350-400 sq ft/gallon). Multiply by number of coats. Add 10% waste. Example: 12x10x8 room with 1 door, 2 windows, 2 coats = about 3 gallons.

Most interior paints cover 350-400 sq ft per coat (one gallon). Higher-quality paints may cover 400-450 sq ft. Rough or porous surfaces (new drywall, stucco, brick) absorb more: 300 sq ft/gallon. Always check the manufacturer label for actual coverage.

Yes in these cases: New drywall or unpainted surfaces. Drastic color changes (dark to light). Stains, repairs, or water damage. Shiny surfaces being repainted. Primer improves adhesion, evens out surface porosity, and can reduce the number of paint coats needed. Self-priming paint claims to combine both.

Flat/matte: no sheen, hides imperfections well. Best for ceilings and low-traffic walls. Eggshell: slight sheen, slightly washable. Good for living rooms. Satin: medium sheen, more washable. Best for hallways, kids rooms. Semi-gloss: shinier, very washable. Best for trim, doors, bathrooms. High-gloss: highest sheen, most durable. Best for trim.

Latex/water-based paint: 10 years if stored properly (sealed, room temperature, never frozen). Oil-based paint: 15 years. Signs it has gone bad: lumpy, stringy, won separated with stirring, or smells very sour. Store paint cans upside-down initially to create a seal, then upright. Never store in freezing temperatures.