The number printed on a paint can — usually "350–400 sq ft" — is a best-case estimate, not a guarantee. Real coverage depends on what you're painting over, how porous the surface is, and whether you're changing colors. Here's how to get a number you can actually trust.
The Standard Coverage Rate
Most interior latex and acrylic paints cover 350–400 sq ft per gallon, per coat, on a smooth, previously painted, primed surface. This is the number manufacturers test under ideal conditions — smooth wall, single even coat, no absorption issues.
Wall area to paint = (2 × (Length + Width) × Height) − doors − windows
Gallons needed = Wall area ÷ 350 (per coat)
What Actually Changes Real-World Coverage
| Factor | Effect on Coverage |
|---|---|
| New, unprimed drywall | Absorbs more paint — expect 20–30% less coverage on the first coat |
| Textured surfaces (popcorn, stucco) | Rougher surface area needs 15–25% more paint |
| Dark-to-light color change | Reduces effective coverage; may need a tinted primer or extra coat |
| Glossier sheen (semi-gloss, gloss) | Similar coverage rate but shows roller marks more if under-applied |
| Spray application | Uses 20–30% more paint than roller due to overspray |
One Coat vs. Two Coats
Two coats is standard for any real color change and is what most professional painters apply by default. A second coat doesn't use quite as much paint as the first, since it's going over an already-sealed surface rather than raw drywall — plan on roughly 1.8x your one-coat gallon estimate for two coats, not a flat 2x.
Quick Reference: Paint Needed by Room Size
| Room Size | Wall Area (approx.) | 1 Coat | 2 Coats |
|---|---|---|---|
| 10×10 ft, 8 ft ceiling | ~270 sq ft | 1 gallon | 1.5 gallons |
| 12×12 ft, 8 ft ceiling | ~320 sq ft | 1 gallon | 2 gallons |
| 14×16 ft, 9 ft ceiling | ~460 sq ft | 1.5 gallons | 2.5 gallons |
| 16×20 ft, 9 ft ceiling | ~560 sq ft | 2 gallons | 3 gallons |
Ceilings Use a Different Calculation
Ceiling coverage is based on floor area (length × width), not wall perimeter, since there are no doors or windows to subtract. Ceiling paint (usually flat) covers at roughly the same 350–400 sq ft/gallon rate as wall paint on a smooth surface, but textured ceilings can cut that significantly.
Frequently Asked Questions
How many square feet does one gallon of paint cover? On a smooth, primed surface, one gallon covers 350–400 sq ft per coat. New drywall or textured surfaces reduce this.
Do I need more paint for a color change? Yes, especially light-over-dark or dark-over-light. A tinted primer coat can reduce the number of topcoats needed to fully cover the old color.
Does paint sheen affect coverage? Not significantly — flat, eggshell, satin, and semi-gloss all cover at roughly the same rate per gallon. Sheen affects durability and cleanability, not quantity needed.
How much paint do I need for two coats? Multiply your one-coat estimate by about 1.8, not a flat 2x, since the second coat typically covers slightly more efficiently over an already-sealed surface.