Reference data
Paint coverage by surface
What a gallon really covers on each substrate, first coat and later coats, against the figure printed on the tin.
Written and edited by Pablo Ruiz Quintero
Last reviewed 2026-09-16
How many square feet does a gallon of paint cover?
About 400 — on a smooth, sealed, previously painted wall. That is the manufacturer’s figure and it is a best case, not an average. On everything else the first coat covers less, sometimes half as much.
| Painting over | First coat | Later coats | Primer | Why |
|---|---|---|---|---|
| Previously painted, similar colour | 400 ft² | 400 ft² | Optional | The condition the spread rate on the tin assumes. Two coats and you are done. |
| Previously painted, big colour change | 380 ft² | 400 ft² | Yes | Going light over dark, or covering a strong colour. Tinted primer beats a third coat of finish paint, and costs less. |
| New drywall | 200 ft² | 380 ft² | Yes | Bare paper and joint compound absorb at completely different rates. Without primer the joints show through as a dull pattern the paint cannot fix. |
| Textured walls or ceiling | 300 ft² | 320 ft² | Optional | Knockdown and orange peel add real surface area you cannot see. Expect a quarter more paint than the flat equivalent. |
| Bare wood | 220 ft² | 360 ft² | Yes | Wood keeps absorbing until it is sealed, and knots bleed through anything that is not a stain-blocking primer. |
| Masonry, brick or stucco | 180 ft² | 300 ft² | Yes | The most absorbent surface here by a distance. Porous, rough and thirsty — budget roughly double the smooth-wall figure. |
Two coats, by room and by surface
| Room | Wall area | Previously | Previously | New | Textured |
|---|---|---|---|---|---|
| 10 × 12 ft, 8 ft ceiling | 301 ft² | 1.5 | 1.5 | 2.3 | 1.9 |
| 12 × 14 ft, 8 ft ceiling | 365 ft² | 1.8 | 1.9 | 2.8 | 2.4 |
| 14 × 18 ft, 9 ft ceiling | 525 ft² | 2.6 | 2.7 | 4.0 | 3.4 |
| 20 × 24 ft, 9 ft ceiling | 741 ft² | 3.7 | 3.8 | 5.7 | 4.8 |
Why the first coat is the one that matters
A porous surface absorbs paint rather than holding it on top. New drywall is the clearest case: bare paper and dried joint compound take up paint at completely different rates, so the first coat is partly disappearing into the wall and partly sitting on it.
Once that coat has sealed the surface, the second behaves normally — which is why the two columns converge. Averaging them into one number, which is what every rule of thumb does, understates the first coat and overstates the rest. The total is close; the day you run out is not.
Texture is area you cannot see
Knockdown and orange peel finishes add real surface area. The wall measures the same and the roller covers about a quarter less of it, which is the same effect as painting a larger room. Heavier textures such as popcorn ceilings take half as much again.
Garage floor epoxy, for comparison
A two-part epoxy kit covers about 250 square feet, and that is the easy part of the calculation. About 60 per cent of a professional floor coating job is grinding the slab so the coating has something to key into — and a slab that has not been ground is why failed garage floors peel in sheets rather than wearing out.
Using it
The paint calculator applies these rates automatically, counts the coats separately, subtracts doors and windows, adds primer where the surface needs it, and prices trim in quarts rather than gallons.
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About the author
Pablo Ruiz Quintero — Editor
Editor of MaterialsEstimator. Decides which documents count as a source, what every default value is, and where the line sits between what the reader parses and what the engines compute.
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