How Much Paint Do I Need for a Room? (Simple Formula & Chart)

The Simple Paint Coverage Formula

Here is the formula: (Perimeter × Ceiling Height - Door & Window Areas) × Number of Coats ÷ 350 = Gallons Needed. One gallon of paint covers approximately 350 square feet on smooth, primed surfaces.

For a standard 12×12 room with 8-foot ceilings, one door, and two windows: (48 ft perimeter × 8 ft height) - 21 sq ft door - (2 × 15 sq ft windows) = 333 sq ft. With two coats: 333 × 2 = 666 sq ft ÷ 350 = 1.9 gallons. Round up to 2 gallons.

Paint Coverage Chart by Room Size

8×10 room (8' ceilings): ~1.5 gallons for 2 coats — buy 2 gallons.

10×10 room: ~1.7 gallons for 2 coats — buy 2 gallons.

10×12 room: ~2.0 gallons for 2 coats — buy 2 gallons.

12×12 room: ~1.9 gallons for 2 coats — buy 2 gallons.

12×14 room: ~2.3 gallons for 2 coats — buy 3 gallons (or 2 gallons + 1 quart).

14×16 room: ~2.8 gallons for 2 coats — buy 3 gallons.

16×20 room: ~3.5 gallons for 2 coats — buy 4 gallons.

These estimates assume standard 8-foot ceilings, one door, and two windows per room. Add 1 gallon for vaulted or 9-10 foot ceilings.

Factors That Affect Paint Coverage

Wall texture is the biggest variable. Smooth drywall gets 350-400 sq ft per gallon. Orange-peel texture drops to 300-350 sq ft. Heavy knockdown or popcorn texture may only get 200-250 sq ft per gallon because the texture absorbs more paint.

Primer matters enormously. Unprimed new drywall absorbs paint like a sponge — you might need 3 coats without primer vs. 2 coats with it. A good primer ($25-$35/gallon) actually saves money by reducing the number of topcoats needed.

Color changes require extra paint. Going from a dark wall to a light color (or vice versa) typically requires 3-4 coats, not 2. Using a tinted primer matched to your topcoat color can reduce this to 2 coats and save a gallon or more.

Paint Quality: Is Expensive Paint Worth It?

Premium paint ($40-$70/gallon) from brands like Benjamin Moore, Sherwin-Williams, or Behr Ultra provides noticeably better coverage, durability, and color richness compared to economy paint ($20-$30/gallon).

Higher-quality paints contain more pigment and resin, which means: better coverage per coat (sometimes one coat is sufficient), longer life (8-10 years vs. 3-5 years), better stain resistance, and easier touch-ups.

The math often favors premium paint. If economy paint requires 3 coats at $25/gallon (3 gallons = $75) and premium paint requires 2 coats at $50/gallon (2 gallons = $100), the premium paint costs slightly more but saves hours of labor and lasts twice as long.

Choosing the Right Finish

Flat/Matte: Best for ceilings and low-traffic rooms. Hides imperfections but is harder to clean. Coverage is usually the best of all finishes.

Eggshell: The most popular wall finish. Slight sheen, easy to clean, and hides minor imperfections. Ideal for living rooms, dining rooms, and bedrooms.

Satin: More sheen than eggshell, excellent durability. Great for hallways, kids' rooms, and any high-traffic area.

Semi-Gloss: Moisture-resistant and very durable. The standard choice for kitchens, bathrooms, and trim work. Shows wall imperfections more than flatter finishes.

Gloss: Maximum durability and moisture resistance. Used primarily for trim, doors, and cabinets. Requires the most wall preparation as it highlights every imperfection.