Question 1

How much paint do I need for a 12x12 room?

Accepted Answer

A 12x12 room with 8-foot ceilings has about 384 square feet of wall area (12+12+12+12 = 48 linear feet x 8 ft = 384 sq ft). Subtract one door (20 sq ft) and one window (15 sq ft) = 349 sq ft of paintable wall. At 350 sq ft per gallon (smooth drywall), you need 1 gallon per coat, or 2 gallons for 2 coats. Add 1 quart of primer if the walls are bare drywall or a dramatic color change.

Question 2

How many square feet does one gallon of paint cover?

Accepted Answer

One gallon of latex paint covers about 350 square feet on smooth, primed drywall. On textured or porous surfaces (popcorn ceilings, stucco, raw wood, brick), coverage drops to 200-300 sq ft per gallon. On dark colors over light primer, you may need 3 coats instead of 2. Oil-based paint covers slightly more per gallon (around 400 sq ft) but dries slower and has stronger fumes.

Question 3

Do I need primer?

Accepted Answer

Yes, in most cases. Primer is required when painting bare drywall, new wood, bare metal, or when switching from a dark to a light color (or vice versa). One coat of quality primer (Kilz, Zinsser, or the paint brand's own primer) covers about 300-350 sq ft per gallon. Many modern 'paint and primer in one' products skip this step for repaints over similar colors but still benefit from a separate primer for dramatic color changes, stains, or porous surfaces.

Question 4

How do I calculate paint for an exterior house?

Accepted Answer

For exterior paint, measure the perimeter of the house (linear feet around the foundation), multiply by the average wall height (typically 8-10 feet for one story, 18-22 for two), then subtract the area of windows and doors (each window averages 15-20 sq ft, each door 20-25 sq ft). For a 1,500 sq ft single-story ranch with 200 linear feet of wall and 9 ft ceilings, that's about 1,800 sq ft minus 200 sq ft of openings = 1,600 sq ft of paintable area, requiring 5 gallons of exterior paint per coat.

Question 5

How much paint do I need for trim and doors?

Accepted Answer

Trim and doors are calculated by linear feet, not square feet. A gallon of trim paint covers about 400 linear feet of 4-inch wide baseboards, door casings, and crown molding. For an average 12x12 room with about 50 linear feet of trim and 1 door, you need about 1 quart of trim paint per coat. Doors themselves: each side of a standard 32-inch door is about 21 sq ft (3 ft x 7 ft), so a gallon covers 2-3 doors per coat, both sides.

Question 6

What's the difference between interior and exterior paint?

Accepted Answer

Interior paint is formulated for stain resistance, washability, and low odor (zero-VOC formulas available). Exterior paint is formulated for UV resistance, flexibility (to handle temperature changes and moisture expansion), and mildew resistance. Never use interior paint outside - it will fade, peel, and chalk within 1-2 years. The reverse (exterior paint inside) is technically safe but the mildewcides and high-VOC formula make it smell bad and off-gas in enclosed spaces.

Question 7

How do I calculate paint for a ceiling?

Accepted Answer

For a flat ceiling, multiply length x width to get the square footage. A 12x12 bedroom ceiling is 144 sq ft, which needs about half a gallon per coat (350 sq ft/gal). For textured or popcorn ceilings, plan for 200-250 sq ft per gallon due to the irregular surface absorbing more paint. Most ceilings are painted with flat or matte finish (hides imperfections better) and need 2 coats if going from a dark to light color, or 1 coat for a refresh over the same color.

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