How Many Square Feet Does a Gallon of Paint Cover?
A gallon of interior paint covers 250 to 400 square feet in a single coat. That 150-square-foot spread is not the manufacturers hedging; it is the wall talking. Paint never spreads at a fixed rate — it spreads at whatever rate the surface allows. Smooth drywall with an existing coat of paint is essentially sealed, so a fresh gallon glides out toward 350 or even 400 square feet. Texture multiplies the actual surface area your roller has to wrap around, and porous surfaces — bare drywall, brick, stucco — drink paint before it ever forms a film. Either condition drags you down toward 250.
My default for planning is 350 square feet per gallon on smooth, previously painted walls, adjusted downward for anything rougher. Every guide on this site uses that same baseline, and so does our paint calculator, so the figures below will agree with whatever the tool tells you.
Coverage by surface
| Surface | Realistic coverage per gallon, one coat |
|---|---|
| Smooth, previously painted drywall | 350–400 sq ft |
| Textured walls (orange peel, knockdown) | 250–325 sq ft |
| Bare, unprimed drywall | 250–300 sq ft (prime it instead — see below) |
| Brick or stucco | About 250 sq ft — the bottom of the range |
| Smooth ceilings | 325–375 sq ft |
| Textured or popcorn ceilings | 250–300 sq ft |
Three things are worth flagging in that table. “Textured” covers a wide spectrum: a light orange peel only trims your coverage a little, while a heavy knockdown or sand-finish wall parks you at the bottom of its band. Bare drywall is listed mostly as a warning — paint soaks into raw paper and joint compound unevenly, so the smarter move is a coat of primer first. And masonry is brutal on coverage because mortar joints and surface pores add square footage you cannot see from across the room; budget the full low end and be pleasantly surprised if a gallon stretches further.
Why the can says 400 but you should plan on less
Flip over almost any gallon of interior wall paint and you’ll find a claim of 350 to 400 square feet. That number is real — under test conditions. It assumes the paint goes on at its ideal film thickness, on a smooth and fully sealed surface, with nothing lost along the way.
Your hallway is not a test condition. The gap comes from a handful of places:
- Texture adds hidden area. A wall that measures 100 square feet on your tape presents more than 100 square feet of paintable surface once the roller has to follow every bump and crater.
- Porosity steals the first pass. Unsealed or chalky surfaces absorb paint instead of letting it sit on top, which is why first coats on bare walls always run short.
- Cutting in double-dips. The brushed band around trim, corners, and the ceiling line gets overlapped by the roller, so a few inches of every edge is effectively painted twice.
- Rollers and trays keep a cut. A 3/8-inch nap cover and the tray it sits in hold a real amount of paint that never reaches the wall.
- DIYers roll heavy. Most of us lay down a thicker film than the spec sheet assumes, especially when we’re nervous about an old color peeking through.
My rule: treat the can’s claim as a ceiling. Use 350 for smooth repaints, and drop to the 250–300 range the moment texture or a bare surface enters the picture.
The hallway that taught me this
Last spring I repainted our upstairs hallway, which has a knockdown texture the builder apparently applied with enthusiasm. The space is 20 feet long with 9-foot ceilings: two long walls at 180 square feet each, plus an end wall around 31, minus four doorways at the standard 21 square feet apiece. Call it 308 square feet of actual wall.
One gallon at the 350 rate should have handled the first coat with paint to spare. Instead the can went dry at roughly 250 square feet — nearly 60 square feet of hallway still showing the old greige while I scraped the tray with the roller trying to stretch it. Back to the store. Two coats on that hallway meant roughly 615 square feet of coverage, and at the 250-per-gallon rate the texture actually allowed, the job needed about 2.5 gallons — three cans. At $44 a gallon, the hallway cost $132 in paint instead of the $88 I had budgeted for a two-gallon job. The texture billed me an extra $44, plus a second trip across town with wet roller covers wrapped in a grocery bag.
Running the numbers on your own room
Measure the perimeter, multiply by ceiling height, then subtract 21 square feet per door and 15 per window. A 13×15 bedroom with 8-foot ceilings works out like this: the perimeter is 56 feet, so 448 square feet of gross wall. Take off two doors (42) and one window (15) and you’re at 391 square feet per coat — 782 for two coats.
On smooth walls at 350 per gallon, that’s 2.23 gallons: two gallons plus a quart, with the quart mostly going to cut-in. On a textured version of the same room at 250, the total becomes 3.13 gallons — past three cans. Same room, same color, a whole extra gallon, purely because of the surface.
Baseboard is a small add-on: figure half a square foot of paintable area per linear foot of trim, so 56 feet of baseboard comes to about 28 square feet — a quart of trim paint handles it with room to spare. For a complete worked example, including the second-coat decision, see the 12×12 room guide.
Primer runs shorter than paint
Primer covers about 300 square feet per gallon — less than topcoat, because it’s built to soak in and seal rather than ride on the surface. For the 429-square-foot bedroom above, one coat of primer is 429 ÷ 300 = 1.43 gallons; a gallon and two quarts covers it, or a second gallon if the wall is thirsty. The payoff is that your paint then behaves like it’s on sealed drywall and hits its full 350-per-gallon stride instead of disappearing into the paper.
Round up, always
The rates in this guide are planning figures, not promises — your roller nap, your wall’s history, and how hard you press all get a vote, which is why I quote bands instead of single numbers. So round every total up to the next can and keep the receipt. An unopened gallon goes back to the store in five minutes; a Saturday afternoon with 60 square feet of bare wall and an empty tray does not.