How much area does 1 gallon of paint cover?

One gallon of paint typically covers 350–400 square feet on a smooth, primed surface with one coat. Rough or porous surfaces may only get 250–300 square feet per gallon.

How many gallons of paint do I need for a 12x12 room?

A 12×12 room with 9 ft ceilings has approximately 432 sq ft of wall area (minus doors and windows ≈ 390 sq ft). For two coats, you would need approximately 2.25 gallons — round up to 3 gallons to be safe.

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🛠️ Construction & DIY

Paint Gallon Estimator

Estimate the number of paint gallons needed for walls and ceilings based on room dimensions and coats.

⚡ Instant 🆓 Free 🔒 Private

paint gallons room walls coats coverage

Room Length (ft)

Room Width (ft)

Ceiling Height (ft)

Number of Coats

Doors (standard)

Windows (standard)

Include 10% Waste Buffer

How Many Gallons of Paint Do You Need?

Paint coverage varies by brand and surface texture, but the industry standard is approximately 350–400 square feet per gallon for a single coat on a smooth, primed surface. Rough or porous surfaces require more paint. Always buy an extra quart for touch-ups.

The Paint Calculation Formula

Paintable Area (ft²) = Total Wall Area − Door Area − Window Area

Total Wall Area = 2 × (Length + Width) × Ceiling Height

Gallons = (Paintable Area × Number of Coats) ÷ 350

Flat vs. Eggshell vs. Semi-Gloss

Paint sheen affects durability and washability, not coverage. Flat paint hides imperfections well but is harder to clean, making it better for ceilings and low-traffic walls. Semi-gloss is ideal for trim, kitchens, and bathrooms where moisture and scrubbing are common.

Paint Gallon Estimator

Gallons of Paint Needed

How Many Gallons of Paint Do You Need?

The Paint Calculation Formula

Flat vs. Eggshell vs. Semi-Gloss