Wall Paint Calculator

By Vinod Kondeti · Updated October 14, 2026

Painting an accent wall or a few matching walls? You often need less than a gallon, and a quart (a quarter gallon) may be enough. This calculator rounds to quarts so you do not overbuy.

Wall width (ft)Wall height (ft)Number of walls (walls)Coats (coats)Coverage per gallon (from label) (ft²)Add one coat of primerPrimer coverage per gallon (from label) (ft²)

Doors & windows (sizes are editable)

Doors (count) (doors)Area per door (edit) (ft²)Windows (count) (windows)Area per window (edit) (ft²)Other areas to skip (ft²)

Cost estimate (optional, enter your local prices)

Paint price per gallon ($)Primer price per gallon ($)

Paintable area (ft²)	–
Paint gallons needed	–
Paint to buy	–
Primer gallons	–
Primer to buy	–
Estimated cost (whole gallons)	–

Working: –

How do I measure for a walls project?

Set the number of walls for matching walls, for example both sides of a hallway.
Bold colours may need an extra coat. Check the can.
Primer usually has a different coverage. Enter the primer label's figure if you are calculating primer.

How is the walls amount calculated?

Room walls = 2 × (length + width) × height − doors & windows (+ length × width for the ceiling)
Gallons = area × coats ÷ coverage per gallon (default 350 ft²)
To buy = gallons rounded up to whole quarts (4 qt = 1 gal)
Exterior = perimeter × wall height + gables × ½ × width × height − openings
Openings = doors × area per door + windows × area per window + other
Primer (optional) = one coat: area ÷ primer coverage
Cost = whole gallons × your $/gal (paint + primer)

Walls calculator questions

How much paint for one 12 × 8 wall, 2 coats?

96 ft² × 2 ÷ 350 = 0.55 gal, so 3 quarts.

Is a quart enough for an accent wall?

Only for small walls. One quart covers about 87 ft² per coat at 350 ft²/gal.

Sources

Estimates only. Use the coverage or bag size printed on your product. Read the paint guide for worked examples.