Paint coverage per gallon: what nine data sheets actually say

A gallon of interior wall paint is rated for 350 to 450 square feet, going by most makers’ data sheets, and Behr prints a wider 250 to 400. That coverage number says more about how thick a coat the maker assumed than about the paint itself. Benjamin Moore’s Aura claims 350 to 400, near the bottom of the pack, yet it would cover the most wall of the nine if they all went on equally thick. Plan a room at 350. It’s the safer number, and it’s where our paint calculator starts.

The math behind the number on the can

Every paint data sheet ties its coverage to a wet film thickness, measured in mils (thousandths of an inch). Behr’s sheet for Premium Plus eggshell lists 400 square feet per gallon at 4.0 mils wet, and 250 at 6.4 mils. Multiply either pair and you get 1,600. That’s a gallon spread out: a US gallon is 231 cubic inches, and laid down one thousandth of an inch thick it covers about 1,604 square feet. So a can that promises 450 is assuming a wet coat of about 3.6 mils. One that promises 250 assumes 6.4.

Then the water leaves. What stays on the wall is the solid part of the paint, and the sheet gives that share as “volume solids.” Sherwin-Williams’ SuperPaint satin sheet puts it on at 4 mils wet and says it dries to 1.5 mils, because the paint is 38% solids (4 × 0.38 = 1.52). That dry layer is what covers the old color.

Put the two together and there’s a fairer question than “how many square feet?” How far does a gallon go if every paint leaves the same dry coat? We picked 1.6 mils, a dry coat several of these sheets list, and worked it out as 1,604 × volume solids ÷ 1.6.

Nine paints on one yardstick

Interior eggshell or satin, from each maker’s technical data sheet. All nine were read on October 8, 2026.

The right-hand column is our arithmetic, not the makers’. The sheets are SuperPaint form 101.11C (header dated 08/2026), Emerald form 101.08SAB (11/2023), Behr Premium Plus (05/25), Behr Ultra Scuff Defense (revised 11/2020) and both Valspar sheets (revised May 15, 2023). The Benjamin Moore sheets carry the footer codes N524 US 031825, N549 US 040125 and N626 US 091824. Seven of the nine give volume solids as plus or minus 2 points, so a point or two between SuperPaint, ben and Emerald is noise. Eight points, 38% against 46%, is real.

Benjamin Moore’s ben and Regal Select both claim 400 to 450 square feet. Aura claims only 350 to 400, yet it has the most solids of any paint here. That’s backwards from the labels. The film column explains it: Benjamin Moore expects Aura on at 4.0 to 4.6 mils wet, and ben at 3.6 to 4.0. Aura’s sheet also says the paint “sometimes makes one-coat coverage achievable,” while still recommending two coats.

So if you’re weighing two cans on price, we’d divide the price by the volume solids and ignore the coverage claim. It’s the closest thing on the sheet to how much paint you’re actually paying for. One limit: equal mils don’t promise equal hiding, since pigment matters too, and none of these sheets gives a hiding figure. Valspar’s two sheets both warn that deep or bright colors “may require an additional coat.”

A 12 by 14 bedroom at four coverage rates

Take a 12 by 14 foot room with 8 foot walls, one door and two windows. That’s 416 square feet of wall, minus 20 for the door and 12 for each window (the sizes our paint calculator counts), so 372 to paint. Two coats make it 744 square feet.

The last column is what our paint calculator would tell you to buy; it rounds three quarts up to a whole gallon. Going from 400 to 450 changes nothing on the shopping list. At 350, add a quart. What adds a whole gallon is planning at Behr’s low end of 250, and whether you need that depends far more on your walls than on the brand on the can.

Your walls move it more than the label

Benjamin Moore ties spread rate to “surface texture and porosity.” The Behr sheets name “application method and substrate porosity,” and leave out paint lost to spraying. Valspar puts it as “surface conditions and application technique may impact coverage.” Behr’s own range, 250 to 400, is three times the gap between the highest claims in the table (400 against 450).

Our reading, not the sheets’: smooth, previously painted walls in a similar color are where the top of a range is realistic, and bare drywall, patches, texture or a big color change pull you toward the bottom. The SuperPaint sheet says priming plus two coats at the recommended thickness “can help” where new drywall or hiding an old color is a factor, and that primer improves hiding on a drastic color change. Benjamin Moore recommends two coats on bare surfaces. If you’re hanging new walls first, the drywall calculator takes the same room size and counts sheets, joint compound and screws.

Two numbers on the Valspar Signature sheet don’t agree. It lists 4.0 mils wet and 2.0 mils dry at 43% solids, but 4.0 × 0.43 is 1.7. One of them is off, and we used the solids figure for our column. Its metric line gives 27 to 37 square meters per 3.78 liters, which works out to about 290 to 400 square feet, a much wider range than the “400 sq. ft. per gallon” printed beside it.

Put your room into the paint calculator. It starts at 350 square feet per gallon. Type in the number from your can if your walls are smooth and already painted, or drop it toward 250, the bottom of Behr’s range, for bare or textured walls. Rooms that aren’t simple rectangles are easier to measure wall by wall in the square footage calculator.