Exterior Paint for a 1,500-Sq-Ft House: Measure the Walls

By Sam Whitaker · Updated 2026-09-06

Worked scenarios are illustrative composites. Our editorial pen name and method.

“It’s a 1,500-square-foot house” feels like it should answer “how much exterior paint do I need?” — and it doesn’t, not even close. That 1,500 is floor area, and paint goes on walls. Worse, two houses with the identical 1,500-square-foot floor plan can need wildly different amounts of paint depending on whether that floor is spread across one story or stacked into two. Before you can trust a gallon count, you have to stop thinking about the floor and start measuring the elevations.

The same floor area, two very different paint jobs

Watch what one variable does. Take 1,500 square feet as a single-story ranch versus a two-story house:

• One-story ranch, roughly 50 × 30 footprint: perimeter ≈ 160 ft, 9-ft walls → about 1,440 sq ft of body wall.
• Two-story house, roughly 27 × 28 footprint (750 sq ft per floor): perimeter ≈ 110 ft, but ~18 ft of stacked wall → about 1,980 sq ft of body wall.

Same floor area, and the two-story has nearly 40% more wall to paint. Then add the gable ends the roof creates, and the gap widens further. This is the whole reason a floor number is useless for paint: it hides the two things that actually set the area — perimeter and height.

Measure elevations, not floor plans

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

1. Measure the width and wall height to the eave for each face: width × height.
2. Add each gable (the triangle under a roof peak) as base × rise ÷ 2.
3. Add any dormers, bump-outs or returns that get painted.
4. Subtract the measured area of large openings — big windows, garage doors — where your estimating method calls for it. Skip the tiny stuff.
5. Keep trim, doors and shutters on separate lines; they are usually a different product and color.

Sum the body-wall area across all four elevations. For our one-story example, say the two end gables add 30 ft × 8 ft ÷ 2 = 120 sq ft each, so 1,440 + 240 = 1,680 sq ft gross, less roughly 150 sq ft of doors and big windows = about 1,530 sq ft of body to coat.

Turning area into gallons — carefully

Exterior surfaces are where the smooth-versus-rough problem bites. A tape measure sees a flat 1,530 square feet, but lap siding, rough cedar, stucco or a heavy profile has more actual surface and lower effective spread. A body-paint rate that hits 350 sq ft/gal on smooth siding might behave more like 300 — or less — on a textured wall.

Body gallons = net wall area × coats ÷ effective coverage

For an illustrative two-coat plan over 1,530 sq ft at 300 sq ft/gal, 1,530 × 2 ÷ 300 = 10.2 gallons. That requires 11 whole gallons, or 10 gallons plus 1 quart if both package sizes are available, before any extra loss allowance. At an assumed 400 sq ft/gal, the same area and coats require 7.65 gallons. These are sensitivity inputs, not established coverage rates for all siding; use the exact product and surface guidance and calculate trim and any primer separately.

Manufacturer guidance treats exterior coverage as product- and condition-dependent for this reason:

• Sherwin-Williams painting application FAQs
• Sherwin-Williams paint calculator

Exterior takeoff shortcuts that fail

• Quoting a range from the floor size. “8 to 15 gallons for a 1,500-sq-ft house” is a coin toss; measure the elevations instead.
• Forgetting the gables. Every roof peak adds a triangle of wall, and they add up fast on a house with several.
• Using the smooth-wall spread rate on rough siding. Buy off the cautious end of the range unless a test area proves the paint goes further.
• Blending body, trim and primer. Three products, three coverage numbers, three lines on the list.

Quantity planning cannot specify the coating system

This is quantity planning, not a coating spec. Exterior work carries decisions a calculator cannot make — surface prep, the right primer for bare or failing areas, weather and temperature limits, and safety around old paint on pre-1978 homes. Read the technical data sheet for the exact product, and let a measured test area settle any coverage doubt.

Once the elevations are measured, put the body, trim and primer into the paint calculator as separate lines with their own coverage, so the profile-thirsty body paint never gets averaged against smooth trim. These are general-information estimates, not professional advice.