Paint Calculator

Calculating paint correctly before starting a project prevents the most common and frustrating painting mistake: running out mid-wall with no matching paint available. Paint is mixed in batches, and even the same formula from the same store can have slight color variation between batches (called "dye lots"). Buying all the paint you need at once — from the same batch — ensures a perfectly consistent result.

Standard paint coverage is approximately 350–400 square feet per gallon with one coat on a smooth, previously painted surface. Coverage decreases for: porous or unprimed surfaces (drywall, bare wood) which absorb 20–30% more paint; rough or heavily textured surfaces; very dark or vibrant colors (which require 3 coats over light); low-quality paints with poor pigment concentration.

Calculating wall area: Wall area = 2 × (Length + Width) × Height. Subtract for doors (~21 sq ft each) and windows (~15 sq ft each). For ceilings, calculate separately: length × width. For trim, estimate the linear feet of trim and multiply by the typical trim width (usually 0.5–1 ft).

Paint finishes and where to use them: Flat/Matte: low sheen, hides imperfections, difficult to clean — best for ceilings and low-traffic areas. Eggshell: slight sheen, somewhat washable — most popular for living rooms and bedrooms. Satin: noticeable sheen, good washability — ideal for kitchens, bathrooms, and hallways. Semi-gloss: shiny, very washable, moisture-resistant — best for trim, doors, and bathrooms. High-gloss: maximum sheen and durability — for trim and cabinets where you want maximum durability.

Primer: always prime new drywall, major color changes (dark to light), stained areas, and bare wood. Primer improves adhesion, reduces paint absorption, and often means you need one fewer topcoat — saving money overall.