How Much Paint Do I Need for a Room?

Quick answer: One gallon of paint covers about 350–400 square feet. For a standard 12×12 room with 8-foot ceilings, you need roughly 1.5 gallons for walls only (one coat) — so buy 2 gallons for two coats.

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The Formula (Step by Step)

Calculate wall area — add up the length of all walls, multiply by ceiling height. For a 12×12 room: (12+12+12+12) × 8 = 384 sq ft
Subtract openings — standard door ≈ 21 sq ft, standard window ≈ 15 sq ft
Divide by coverage rate — 350 sq ft per gallon for most latex paint
Multiply by number of coats — usually 2
Round up — paint is sold in gallons and quarts

Real Example: 12×14 Bedroom

Walls: (12+14+12+14) × 8 = 416 sq ft
Minus 1 door (21) and 2 windows (30): 365 sq ft
365 ÷ 350 = 1.04 gallons per coat
Two coats: 2.08 gallons → Buy 2 gallons + 1 quart (or just 3 gallons to have touch-up paint).

Paint Coverage by Type

Flat/matte latex: 350–400 sq ft/gallon
Eggshell/satin: 350–400 sq ft/gallon
Semi-gloss: 350–400 sq ft/gallon
Primer: 200–300 sq ft/gallon (thicker, more absorbent surfaces)
Ceiling paint: 350–400 sq ft/gallon

Important: These are manufacturer claims on smooth, primed surfaces. Textured walls, bare drywall, or dark-to-light color changes use 20–30% more paint.

Do I Need One Coat or Two?

Almost always two. One coat is enough only if you're painting the exact same color. Otherwise:

Light over light: 2 coats
Dark over light: 2–3 coats
Light over dark: Tinted primer + 2 coats
New drywall: Primer + 2 coats

Common Mistakes to Avoid

❌ Buying exactly what you calculated

Always round up. Having leftover paint for touch-ups is worth far more than a second trip to the store — especially after they custom-mix your color.

❌ Skipping primer

Primer isn't optional on new drywall, stains, or dramatic color changes. It saves you a coat of expensive paint and gives better adhesion.

❌ Forgetting the ceiling

If you're painting the ceiling, add that square footage separately. Ceilings typically need their own flat white paint.

❌ Not accounting for texture

Knockdown or orange peel texture can increase paint consumption by 20–30% compared to smooth walls. Rough brick or stucco can double it.

Pro Tips

Keep the label. Write the room name on the can lid. When you need touch-up paint in 2 years, you'll thank yourself.
Buy all at once. Color can vary slightly between batches. Get all your gallons from the same mix if possible.
One gallon is often enough for a bathroom or small closet (two coats).
Trim paint: Budget about 1 quart per room for baseboards, window frames, and door casings.

Frequently Asked Questions

How many gallons do I need for a 1,500 sq ft house?

A rough estimate for interior walls is 12–15 gallons (two coats, accounting for openings). It depends heavily on room layout and ceiling height, so calculate each room separately for accuracy.

Does paint color affect coverage?

Yes. Deep reds, yellows, and bright colors often need an extra coat. Many paint brands now offer "one-coat" lines with higher pigment density — they cost more but save time.

How much paint do I need for a ceiling?

Just the floor area of the room. A 12×14 room ceiling = 168 sq ft = about half a gallon per coat.

Can I return unused paint?

Most stores accept returns of unopened, unmixed cans. Custom-tinted paint usually can't be returned — another reason to calculate carefully.

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