How Much Paint for a 1,500 Sq Ft House Exterior? Floor Size Isn't Wall Size
The first thing I tell anyone planning to repaint their siding: that “1,500 square feet” on your tax record is the floor, and your roller never touches the floor. Two houses can both be 1,500 square feet and one needs 8 gallons while the other needs 14. The difference is geometry, and almost everyone gets it backwards on the first try — including me, the year I bought paint for my brother-in-law’s place off the listing square footage and came up two gallons short on the gable end.
Floor area and wall area are different numbers
Wall area is the perimeter of the house multiplied by how tall the walls stand. Floor area tells you nothing about either of those directly, because a square footprint and a long skinny one can enclose the same floor while presenting wildly different amounts of outside wall.
Take two real ways to build 1,500 square feet:
| House | Footprint | Stories | Perimeter | Wall height | Gross wall area |
|---|---|---|---|---|---|
| Single-story ranch | ~50 ft × 30 ft | 1 | 160 ft | 10 ft | 1,600 sq ft |
| Two-story compact | ~27 ft × 27 ft | 2 | 108 ft | 18 ft | 1,944 sq ft |
Same 1,500 square feet of living space. The ranch wraps 160 feet of perimeter (50 + 30 + 50 + 30) around a single 10-foot story and ends up with 1,600 square feet of wall. The two-story is only 27 by 27 on the ground — 729 square feet per floor, two floors, close enough to 1,500 — so its perimeter shrinks to 108 feet, but it stacks 18 feet tall and reaches 1,944 square feet of wall. The taller house has more paintable surface despite covering less ground. If you’d estimated either one from the 1,500 number, you’d have been wrong in both directions.
That’s the whole trap. A two-story home almost always carries more siding than a sprawling ranch of identical floor size, because vertical surface is cheap to build and expensive to paint.
Now take out the holes
Nobody paints the windows and doors. On a typical house, openings eat 15 to 20 percent of the gross wall — bigger on a place with lots of glass, smaller on a windowless garage-heavy elevation. I use a flat 15 percent when I haven’t measured each opening and 20 percent on a house I know is window-heavy.
Run both example houses at 15 percent off:
| House | Gross wall | Less 15% openings | Net paintable body |
|---|---|---|---|
| Ranch | 1,600 sq ft | −240 sq ft | 1,360 sq ft |
| Two-story | 1,944 sq ft | −291 sq ft | 1,653 sq ft |
Now we have something honest to divide into gallons.
Coverage depends entirely on your siding
This is where exterior work splits from interior. A smooth lap-sided wall sheds paint at a generous rate; rough cedar or a sand-finish stucco drinks it. The texture is the single biggest lever on your gallon count, bigger than the color, bigger than the brand.
| Siding surface | Realistic coverage per gallon, one coat |
|---|---|
| Smooth lap siding, fiber cement, previously painted | 350–400 sq ft |
| Rough-sawn cedar, board-and-batten, T1-11 | 200–250 sq ft |
| Stucco, brick, heavy split-shake | 200–250 sq ft |
That’s not a small swing. The same wall that takes one gallon of smooth-siding coverage can take nearly two gallons if it’s rough cedar, because the roller has to chase every groove and the porous wood pulls the first pass straight in. When I planned my own fiber-cement repaint I worked from 375; when a neighbor did his rough cedar we planned on 225 and still rounded up.
Two coats, and the gallon range falls out
Exterior repaints are almost always two coats — sun, rain, and the old color showing through don’t forgive a single pass. So double the net area, then divide by your coverage rate.
Ranch, smooth siding (375/gal): 1,360 × 2 = 2,720 sq ft ÷ 375 = 7.25 gallons → buy 8.
Ranch, rough cedar (225/gal): 1,360 × 2 = 2,720 ÷ 225 = 12.1 gallons → buy 12–13.
Two-story, smooth siding (375/gal): 1,653 × 2 = 3,306 ÷ 375 = 8.8 gallons → buy 9.
Two-story, rough cedar (225/gal): 1,653 × 2 = 3,306 ÷ 225 = 14.7 gallons → buy 15.
There’s your spread: roughly 8 to 15 gallons of body paint for a 1,500-square-foot house, and which end you land on is set almost entirely by stories and siding texture. If your house is a smooth single-story, plan near the bottom. If it’s a two-story in rough cedar, plan near the top and don’t flinch at it.
If you want the perimeter, opening, and two-coat math handled for you, run your measurements through the paint calculator — but feed it the perimeter and wall height, not the floor square footage, or it’ll be just as wrong as the listing was. The same coverage logic I’m using here is broken down surface by surface in how many square feet a gallon of paint covers, which is worth a read before you settle on your 225 or 375.
Trim is its own bucket — and its own color
Everything above is body paint. Your fascia, soffits, window casings, corner boards, and door frames usually get a different color and a different finish, so they’re a separate purchase. Trim is hard to estimate by area because it’s all edges, but a reliable shortcut on a 1,500-square-foot house is 1 to 2 gallons of trim paint depending on how much detail your house carries. A plain ranch with simple casings sits near 1 gallon; a two-story with deep eaves, lots of windows, and a wrapped porch climbs toward 2.
Put the two buckets together and a realistic shopping list for the two-story rough-cedar case looks like this:
| Bucket | Gallons | Why |
|---|---|---|
| Body | 15 | 1,653 sq ft net × 2 coats ÷ 225 |
| Trim | 2 | Heavy eaves, many window casings, porch |
| Total | 17 | Two separate colors, two separate cans |
Don’t let the trim sneak into the body count or vice versa — they’re different sheens and usually different colors, and you can’t borrow a gallon from one bucket to finish the other.
A calculator can’t see your siding
Here’s the honest limit. I can give you the geometry, the opening deduction, and the coverage bands, but I cannot tell you the one number that matters most: how thirsty your walls are. A calculator can’t feel whether your cedar is rough or weathered-smooth, whether your stucco is fresh or sealed, or whether a previous owner’s chalky old coat is going to suck down an extra half-gallon per side. That’s a tape measure and a hand-on-the-wall job, and it’s yours to do.
So do this before you buy: walk the house and measure the actual perimeter with a tape — the long way around, every jog and bump-out included — and measure your true wall height (a one-story with 9-foot interior ceilings is more than 10 feet of exterior wall once you count the band joist and the gable triangles). Multiply, take off 15 to 20 percent for openings, double for two coats, and divide by the coverage your specific siding earns. If you’re going light over a dark or chalky old color, you may need primer or a third pass on the sunny elevations, and I’d budget for it the same way I’d budget for it indoors — see do you need primer before you assume two coats will bury the old color. And if you’ll be scraping or sanding a chalky pre-1978 coat, treat it as possible lead paint — the EPA recommends testing and lead-safe prep, or a certified painter, before you disturb it.
Round every total up to the next whole gallon and keep the receipts. An unopened can goes back to the store; a half-painted gable at five o’clock with empty cans does not. For a 1,500-square-foot house, expect 8 to 15 gallons of body plus 1 to 2 of trim — and remember the floor square footage had almost nothing to do with how you got there.