HOW MANY SQUARE FEET DOES A GALLON OF PAINT COVER?

One gallon of interior wall paint covers 350 to 450 square feet in one coat on smooth drywall or previously painted walls. That is the spread rate printed on the makers' own sheets: Benjamin Moore lists 400 to 450 sq ft per gallon for Regal Select and 350 to 400 for Aura Matte, and Sherwin-Williams lists 350 to 400 for ProMar 200 Zero VOC.

The label number is for one coat at the film thickness the maker tested. Most repaints get two coats, so a gallon really paints 175 to 225 square feet of wall. Rough, porous or bare surfaces take more paint, and exterior paints are rated lower. To turn a room's size into gallons, the paint calculator does the measuring, the openings and the coats for you.

Every can points to a product data sheet, and that sheet is where the coverage number lives. These are the published spread rates for one coat, read from each maker's product page or data sheet in October 2026.

Exterior paints, primers and masonry coatings have their own rates; they are further down. Behr and Valspar publish coverage on their labels too; read the can or its sheet for the exact product you buy.

A coverage rate is really a thickness spec. Sherwin-Williams's data sheet for ProMar 200 Zero VOC Eg-Shel says 350 to 400 sq ft per gallon at 4 mils wet, which dries to 1.7 mils. A mil is a thousandth of an inch. Multiply the two numbers on the sheet, 400 sq ft × 4 mils, and you get about 1,600: one gallon spread 1 mil thick covers roughly 1,600 square feet.

That one constant explains every coverage claim on the shelf. Roll the same gallon at 5 mils and it covers about 320 sq ft; stretch it to 3 mils and it reaches about 530, but the dry film is a quarter thinner than the coat the maker tested for hide, washability and durability. Painters who “get 500 out of a gallon” of a 400-rated paint are usually laying the film too thin, and the second coat pays for it.

Half the label. A paint rated 350 to 400 sq ft per gallon paints 175 to 200 sq ft of wall in two coats; a 400 to 450 paint, 200 to 225. Benjamin Moore lists “1 or 2” recommended coats on its interior lines, and Sherwin-Williams' ProMar 200 sheet specifies one coat of primer and two coats of finish over new drywall.

One coat is enough only when all of these are true:

• the old paint is sound, clean and close to the new color;
• there are no patches, stains or bare spots to flash through;
• the sheen is staying the same.

A big color change is the other way round. Sherwin-Williams' ProMar 200 sheet notes that “when repainting involves a drastic color change, a coat of primer will improve the hiding performance of the topcoat color.” Budget that primer coat at the primer's own rate; the types of primer guide covers which one to use.

A quart is a quarter of a gallon and a pail is five gallons, so the coverage scales straight from the label. At the two ends of the usual interior range:

Often less than interior paint. Benjamin Moore lists 250 to 350 sq ft per gallon for Aura Exterior and for Regal Select Exterior High Build, both flat. Sherwin-Williams rates its A-100 Exterior Latex Flat at 350 to 400 sq ft at 4 mils wet. Siding, trim and weathered wood are rougher and thirstier than drywall, so plan the low end.

Masonry is where coverage collapses. The Loxon sheet rates 200 to 300 sq ft per gallon at 5.3 to 8.0 mils wet, then adds that porous, rough stucco takes the same gallon only 80 square feet. The stucco painting guide and brick and stone guide cover the prep. For whole-house quantities and prices, see the cost to paint a house. Decks and fences have their own math in the deck stain calculator and the fence paint calculator.

The data-sheet rate assumes a smooth, sealed surface and a coat laid at the listed film. Real jobs fall short of it for five reasons:

• Porous surfaces. Bare drywall paper, fresh joint compound, raw wood and new plaster soak up the first coat. Prime them, and count the primer as its own coat.
• Texture. Knockdown, orange peel and popcorn have more surface than their flat footprint. Loxon's drop from 200–300 to 80 sq ft per gallon on rough stucco is the extreme case; see painting a popcorn ceiling.
• Color change. Deep colors and light-over-dark need more coats, not a thicker one. A tinted primer is usually cheaper than a third finish coat.
• Spraying. Some of every sprayed gallon ends up in the air or on the masking. How much depends on the tip, the pressure and the wind; the spray vs roll comparison covers the trade-off.
• Waste. Paint dried in the tray, the roller cover and the bottom of the can never reaches the wall. On a small room it is a real share of the gallon.

A 12 × 12 ft bedroom with 8 ft ceilings, walls only, two coats. The perimeter is 48 ft, so the walls are 48 × 8 = 384 sq ft. Take off one 3 × 7 ft door (21 sq ft) and two 3 × 5 ft windows (30 sq ft): 333 sq ft to paint. Two coats make it 666 sq ft.

A house with 1,800 sq ft of exterior wall after openings, two coats.That is 3,600 sq ft of coating. At 350 sq ft per gallon it takes about 10.3 gallons; at 250 it takes 14.4. The spread between the two ends of one data sheet is four gallons, which is why a bid states the rate it assumed.

For a contractor, coverage is a material line and a labor line at once: a paint that needs a third coat costs a day, not just a gallon. Four habits keep the material number honest:

1. Price from the low end of the sheet's range. 350 on a 350–400 paint, 250 on a 250–350 exterior. The high end is for a perfect wall.
2. Count each color and sheen separately, then round up. Three colors at 1.2 gallons each is three gallons and three quarts, not 3.6 gallons.
3. Add primer as its own coat at its own rate. New drywall, patches, stains and big color changes all need it.
4. Write the assumption down. “Two coats at 350 sq ft/gal” on the estimate settles the argument when a client picks a deep accent color later.

The painting estimate template has a materials section for these lines, and how to price painting jobs covers the markup on top.