Paint Calculator
How many gallons of paint you need
Painting a room or exterior? Enter the total wall length and height, choose your coats, and we'll tell you how many gallons to buy.
How much paint do I need?
A gallon covers about 350 ft² per coat. Add up all wall lengths, multiply by ceiling height, subtract doors and windows, then multiply by coats.
One coat or two?
Plan on two coats for new drywall, color changes, or dark-over-light.
Don't forget ceilings and trim
This calculator covers your walls. Ceilings, trim, doors and closets are separate — a ceiling adds roughly the room's floor area, and trim paint is usually a different sheen (semi-gloss) bought by the quart. Budget about a quart of trim paint per average room as a starting point.
Buy from one batch
Custom-mixed colors can vary slightly between cans, so buy all your paint at once and "box" it — pour the gallons together into one large bucket and stir — for a seamless color across every wall.
Paint Calculator: frequently asked questions
How much does a gallon of paint cover?
About 350 square feet per coat on smooth, primed surfaces. Rough surfaces cover less.
How many gallons to paint a 12x12 room?
Roughly 1.5–2 gallons for two coats with 8-foot ceilings, before deducting openings.
How much paint for a ceiling?
A ceiling is about the same area as the room's floor, so a 12×12 ceiling (~144 ft²) needs a little under half a gallon per coat. Most people buy a full gallon of flat ceiling paint and keep the rest for touch-ups.