How many square feet does a gallon of paint cover?

Typically about 350–400 sq ft per coat on smooth, primed surfaces, per manufacturer guidance. Check your specific product.

How much paint for a 12×12 room?

Roughly two gallons for two coats on the walls, assuming 8 ft ceilings, one door and two windows. Ceilings and trim are extra.

Do I always need two coats?

Two coats is the usual recommendation for even color, especially for a color change. Repainting the same color over a sound surface can sometimes take one.

Guides · CSL–007

How much paint do I need?

Short answer: Multiply the room perimeter by the wall height, subtract doors and windows, multiply by the number of coats, then divide by your paint's coverage, typically about 350–400 sq ft per gallon on smooth surfaces. Round up. A typical 12×12 ft bedroom with 8 ft ceilings needs roughly two gallons for two coats.

The formula

Wall area = perimeter × height. (12+12+12+12) × 8 = 384 sq ft.
Subtract openings. A common allowance is about 20 sq ft per door and 10–15 sq ft per window. One door and two windows: 384 − 20 − 30 ≈ 334 sq ft.
Multiply by coats. Two coats: 668 sq ft.
Divide by coverage. At 350 sq ft/gal: 668 ÷ 350 ≈ 1.9, so 2 gallons.

Always use the coverage printed on your can or its technical data sheet. Manufacturers commonly list about 350–400 sq ft per gallon on primed, smooth surfaces. Real-world coverage is lower on textured, porous or unprimed surfaces.

Quick reference

Job	Rough amount
Accent wall or door	About 1 quart (covers roughly 100 sq ft)
Primer	Lower coverage, about 200–300 sq ft per gallon
Ceiling	Length × width ÷ coverage, per coat

When you'll need more

Big color changes, especially light over dark or deep colors over light (expect an extra coat or a tinted primer).
Bare drywall, plaster patches or textured walls.
Spraying, which wastes more than rolling.

Before buying gallons, buy samples: see our guide to ordering samples. If your home was built before 1978, read the EPA's lead-paint guidance before sanding or scraping.

Useful supplies

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Laser distance measure: measures walls quickly and accurately. (Search on Amazon)
Paint roller kit: rollers, tray and covers for walls. (Search on Amazon)
Canvas drop cloth: protects floors and is reusable. (Search on Amazon)

FAQ

How many square feet does a gallon of paint cover?: Typically about 350–400 sq ft per coat on smooth, primed surfaces, per manufacturer guidance. Check your specific product.
How much paint for a 12×12 room?: Roughly two gallons for two coats on the walls, assuming 8 ft ceilings, one door and two windows. Ceilings and trim are extra.
Do I always need two coats?: Two coats is the usual recommendation for even color, especially for a color change. Repainting the same color over a sound surface can sometimes take one.

Sources

Sources checked October 23, 2026. Rules of thumb on this page are our editorial guidance, not standards.