Room Paint Calculator

A 12×14 foot room with 8-foot ceilings has 416 sq ft of wall area (perimeter 52 lft × 8 ft height) Subtract roughly 40 sq ft for a door and two windows. This leaves 376 sq ft paintable. At 350–400 sq ft per gallon per coat, you need 1 gallon per coat, or 2 gallons total for standard two-coat coverage. Textured walls and dark-to-light color changes reduce coverage to 250–300 sq ft/gallon, requiring 3 gallons. Buy ceiling paint separately — the 168 sq ft ceiling needs an additional gallon. Round up to the next full gallon; custom-tinted paint cannot be returned.

One gallon of interior acrylic-latex covers 350–400 sq ft per coat on smooth, previously painted drywall. Textured surfaces — knockdown, orange peel, popcorn — drop that to 250–300 sq ft/gallon because texture valleys consume more paint. Primer covers 300–400 sq ft/gallon; ceiling paint at its thicker consistency manages 300–350. These figures assume a 4-mil wet film thickness. Apply too thin (stretching the paint) and you get poor hide with uneven sheen. Higher-solids paints (40–50% by volume) cover better per coat than budget formulas at 30–35% solids, often eliminating that expensive third coat.

Subtract 21 sq ft per standard interior door (3×7 ft) and 15 sq ft per standard window (3×5 ft) from the total wall area. A room with 2 doors and 2 windows saves roughly 72 sq ft — about 1/5 of a gallon per coat. On rooms with many windows (sunrooms, breakfast nooks), the subtraction matters — often 10–15% less paint — and can eliminate an entire gallon from your purchase. However, professional painters often skip the subtraction and use the extra paint for touchups and the additional cutting-in time around frames. This consumes 10–15% more paint per foot than open-wall rolling.

Each sheen trades durability for forgiveness. Flat (0–5% gloss) hides wall imperfections but stains easily — ceilings and low-traffic rooms only. Eggshell (10–25% gloss) is the most popular wall finish: slight sheen, good washability. Satin (25–35% gloss) adds moisture resistance — ideal for kitchens, bathrooms, kids rooms. Semi-gloss (35–70% gloss) cleans easiest and handles moisture best, making it the standard for trim, doors, and cabinets. The tradeoff? Higher sheen reveals every bump, patch, and roller mark. Simple rule: flat on ceilings, eggshell on walls, semi-gloss on trim covers 90% of rooms correctly.

Use two coats for every repaint and three coats for dramatic color changes (adding $0.50–$1.00/sq ft in extra paint) One-coat coverage is a marketing claim that works only in ideal conditions. Same-color refresh on smooth. Previously primed surfaces. In practice, one coat produces uneven coverage visible in raking light (morning or evening sun across the wall surface) Two coats build proper film thickness (3–4 mils dry) for the rated durability and washability. Premium paints with high solids (45–50% by volume) hide better per coat than budget paints (30–35%) but still need two coats for uniform appearance. The cost difference between one and two coats is $0.15–$0.30/sq ft in extra paint — a trivial expense versus the visible quality improvement.