Paint Coverage Calculator
Coverage — the spread rate — is the number that turns square feet into gallons. Enter how many gallons you have and the spread rate, and see how much area they cover in one coat and across your coats.
3 gallons at 350 sq ft/gal covers about 1,050 sq ft in one coat, or 525 sq ft at 2 coats. Coverage (spread rate) is the square feet one gallon covers in one coat — ~350–400 for smooth drywall, less for rough wood, stucco or brick; the can’s stated spread rate wins over any rule of thumb.
Calculator inputs
Every “how much paint” answer rests on one assumption: coverage. It is the square feet a single gallon covers in one coat — high on smooth, sealed drywall (350–400), much lower on rough wood, stucco or bare brick (down to 100–200). This tool works the identity in both directions: how much area your gallons cover, and (in reverse) how many gallons an area needs.
The coverage figures below are the signature coverage-by-surface dataset. Treat them as planning typicals — the spread rate printed on the paint can you actually buy is the real number.
Formula
area covered (1 coat) = gallons × coverage per gallonarea covered (your coats) = gallons × coverage ÷ coatsgallons needed = ceil( area × coats ÷ coverage )
Worked example
Three gallons at 350 sq ft/gal:
- One coat: 3 × 350 = 1,050 sq ft.
- Two coats: 1,050 ÷ 2 = 525 sq ft finished in two coats.
Flip it around: to two-coat 381 sq ft you need ceil(381 × 2 ÷ 350) = 3 gallons — which is exactly what the how-much-paint calculator returns.
Match coverage to the surface
Where coverage estimates go wrong:
- Surface beats product. The same paint covers 400 sq ft on smooth drywall and 150 on bare brick — pick the coverage row that matches your wall, not the best-case on the label.
- Color and coats interact. A dark-to-light change needs more coats, which cuts the area a gallon finishes.
- The can wins. Manufacturers state a spread-rate range; use it over any chart, and expect the low end on porous or thirsty surfaces.
- Leave a margin. Cutting-in, roller loss and touch-ups all eat into the theoretical coverage.
Reference table
| Paint × surface | Coverage (sq ft/gal, one coat) |
|---|---|
| Smooth / previously-painted drywall (latex) | 350–400 |
| New / primed drywall | 300–350 |
| Textured or porous interior wall | 250–300 |
| Smooth wood / trim (enamel) | 350–400 |
| Bare / rough wood | 200–300 |
| Exterior lap / vinyl siding (smooth) | 300–400 |
| Stucco / rough masonry | 150–250 |
| Brick (unpainted) | 100–200 |
| Concrete / block | 200–300 |
| Deck / fence (semi-transparent stain) | 200–300 |
| Primer (drywall / general) | 200–300 |
Labeled published planning snapshot — the can’s stated spread rate wins. Rough, porous or thirsty surfaces sit at the low end; a big color change or a light coat pushes you toward the high end. Full matrix: paint coverage by surface.
Frequently asked questions
How much does a gallon of paint cover?
Roughly 350–400 sq ft in one coat on smooth, sealed drywall. Expect far less on rough or porous surfaces: 200–300 on bare wood, 150–250 on stucco, 100–200 on unpainted brick. The paint can’s stated spread rate is the figure to trust.
What is spread rate?
Spread rate and coverage are the same thing — the area one gallon covers in a single coat. It drops as the surface gets rougher or more porous, and the effective area per gallon falls as you add coats.
Why does my paint cover less than the label says?
Labels quote a best-case on smooth, primed drywall. Texture, porosity, a big color change, cutting-in and roller loss all reduce real coverage. Plan on the low end of the range for anything that is not smooth and sealed.