How Much Exterior Paint for a House: Measure Walls and Gables, Not Floor Area

By Sam Whitaker · Updated 2026-10-04

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“It’s a 1,500-square-foot house” does not tell you how much exterior paint to buy. That number is floor area, and paint goes on walls. Two houses with the same floor area can have very different wall areas depending on how many stories they have, how long their perimeter is and how many gables the roof creates. Before trusting a gallon count, measure the elevations.

This page shows how to measure walls and gables, what the walls of American houses are actually clad in, and how to turn net wall area into gallons with the product’s own spread rate.

Same floor area, different walls

Take 1,500 square feet of floor in two shapes:

One-story ranch, about 50 × 30 feet: a perimeter of about 160 feet and 9-foot walls give about 1,440 square feet of body wall.
Two-story, about 27 × 28 feet (750 square feet per floor): a perimeter of about 110 feet, but about 18 feet of stacked wall, gives about 1,980 square feet.

The two-story has nearly 40 percent more wall to paint before gables are added. Perimeter and wall height set the paint area; floor area hides both.

Houses are also bigger than 1,500 square feet on average now. The median new single-family house completed in 2025 had 2,142 square feet of floor area, according to the Census Bureau’s Survey of Construction. The median was 2,459 square feet in the Northeast, 2,162 in the South, 2,090 in the West and 1,969 in the Midwest.

What the walls are made of

Many exterior walls are not painted at all, so check what your house is clad in before planning a body coat. For new single-family houses completed in 2025, the Census Bureau recorded the primary exterior wall material as follows:

Primary exterior wall material, new houses completed in 2025	U.S.	Northeast	Midwest	South	West
Stucco	26%	1%	under 0.5%	23%	55%
Vinyl siding	26%	70%	64%	21%	5%
Fiber cement	23%	8%	12%	24%	31%
Brick or brick veneer	16%	8%	4%	26%	1%
Wood	6%	11%	16%	3%	7%
Other (stone, concrete block, aluminum and others)	2%	2%	3%	3%	1%

Source: U.S. Census Bureau, Characteristics of New Housing, 2025. Percentages may not add to 100 because of rounding.

Region matters more than the national mix. Seven in ten new houses in the Northeast have vinyl siding, while more than half in the West are stucco. These figures describe houses built recently, not the whole housing stock, but they show which surfaces you are likely to be working with:

Vinyl siding is factory-colored and often not painted. If you do paint it, follow the siding maker’s guidance and use a coating labeled for vinyl; dark colors can absorb heat and warp the panels.
Fiber cement is often factory-primed or prefinished. It takes exterior acrylic paint well, and its smooth or lightly textured faces sit toward the upper end of a product’s coverage range.
Stucco is rough and porous and pulls coverage toward the lower end of the range or below it. Masonry primers or elastomeric coatings have their own spread rates.
Wood siding and trim need sound, dry surfaces and primer where bare. Rough-sawn wood absorbs more than smooth boards.
Brick is usually left unpainted; painting it is a separate decision with its own primer and breathability questions.

Measure each elevation

Walk each side of the house and treat it as a set of shapes:

Measure the width and the wall height to the eave for each face: width × height.
Add each gable, the triangle under a roof peak, using the method below.
Add dormers, bump-outs and returns that get painted.
Subtract the measured area of large openings such as big windows and garage doors. Skip small items.
Keep trim, doors and shutters on separate lines. They are usually a different product and color.

For the one-story example, two end gables each 30 feet wide with an 8-foot rise add 30 × 8 ÷ 2 = 120 square feet apiece. That brings the total to 1,440 + 240 = 1,680 square feet gross. Less about 150 square feet of doors and large windows, about 1,530 square feet of body wall needs paint.

Gables and vaulted walls: a rectangle with a triangle on top

A gable wall, inside or out, is a rectangle with a triangle sitting on it. Draw an imaginary line at the spring line, the height where the slope begins:

Rectangle = wall width × height to the spring line
Triangle = wall width × rise from the spring line to the peak ÷ 2

A 20-foot-wide wall that is 8 feet to the spring line and rises another 6 feet to the peak has a 20 × 8 = 160-square-foot rectangle and a 20 × 6 ÷ 2 = 60-square-foot triangle, or 220 square feet in all. Measure the rectangle only to the spring line. Extending it to the peak and then adding the triangle counts the top twice.

If the peak is off-center or the two slopes differ, split the upper part into two right triangles and measure each one’s base and rise. A vaulted interior ceiling is measured along each sloped plane, multiplied by the room length; it is always larger than the floor beneath it.

Turn wall area into gallons

Body gallons = net wall area × coats ÷ the product’s spread rate

Exterior coverage varies more than interior coverage, because exterior products are designed for different film thicknesses and surfaces vary from smooth fiber cement to rough stucco. Benjamin Moore’s data sheets, for example, list 350–450 square feet per gallon for its Ultra Spec EXT satin and 250–350 for its Aura exterior satin and Regal Select high-build exterior. The paint coverage guide compares more products and explains why thicker coatings cover less.

For two coats over 1,530 square feet:

Spread rate used	Gallons	Whole gallons
400 sq ft/gal	7.65	8
350 sq ft/gal	8.74	9
300 sq ft/gal	10.20	11
250 sq ft/gal	12.24	13

The difference between the high and low cases is five gallons, so use the exact product’s range and plan from its low end on textured siding. Five-gallon pails are often priced below five single gallons, so compare package prices once you know the quantity.

For the 20-foot gable wall above, minus a measured 3 × 5-foot window, the net face is 205 square feet. Two coats at 350 square feet per gallon need 205 × 2 ÷ 350 = 1.17 gallons, which rounds up to 1 gallon + 1 quart where quarts are sold.

What quantity math cannot decide

Exterior work involves decisions that a gallon count cannot make: surface preparation, primer for bare or failing areas, temperature and weather limits printed on the label, and safe handling of old paint. For homes built before 1978, the EPA warns that scraping or sanding old paint can release lead dust and recommends lead-safe work practices. Tall gables usually mean ladders or scaffolding, and access is often the bigger part of the job than the paint.

Put the body, trim and any primer into the paint calculator as separate lines with their own coverage, so a thirsty body coat is never averaged against smooth trim.

Sources

Figures on this page are general-information estimates, not professional advice. Check the stated assumptions and any linked manufacturer or primary sources before buying materials.