One gallon of paint covers about 350 to 400 square feet in a single coat. Manufacturers usually print 400 sq ft on the can. In practice, 350 sq ft is the safer number to plan with.
Because most jobs need two coats, the figure that actually matters is closer to 175 to 200 square feet of wall per gallon.
Why the number on the can is optimistic
The coverage rate printed on a paint can is a laboratory figure: it assumes a smooth, primed, non-porous surface, applied at the manufacturer's recommended film thickness, in conditions nobody's spare bedroom actually meets.
It isn't dishonest. It's just measured under ideal conditions. The gap between 400 and 350 is roughly the difference between a lab panel and a real wall.
What actually changes your coverage
Surface texture
This is the biggest factor and the one people underestimate most. A textured wall has considerably more real surface area than a flat one. Knockdown or orange-peel texture can cut coverage by 20 to 30%, and heavy popcorn ceilings are worse. You're painting every peak and valley, not a flat plane.
Porosity
Bare drywall, new plaster, and raw wood drink paint. The first coat mostly soaks in instead of sitting on top, which is exactly what primer is for: it seals the surface so your (more expensive) finish paint stays where you put it. Skipping primer on bare drywall usually costs more in extra paint than the primer would have.
Color change
Coverage rate and opacity are different things. Going from white to a deep navy may need three coats no matter how good the coverage rate is, while a soft off-white over an existing off-white might genuinely be fine with one. Dark reds and yellows are notoriously the worst offenders, since their pigments are less opaque.
Application method
Rollers are the most efficient. Brushes lay down a thicker film. Sprayers are fastest but lose real material to overspray. Plan for noticeably more paint if you're spraying, particularly outdoors where any breeze carries some away.
Working out your own number
The arithmetic is straightforward. Measure the perimeter of the room, multiply by ceiling height for gross wall area, subtract openings, then divide by coverage rate and multiply by coats:
gallons = (wall area − openings) × coats ÷ 350
A standard interior door takes out about 21 sq ft and an average window about 15 sq ft. For a 12 × 14 ft room with 9 ft ceilings, one door and two windows, that comes out to roughly 417 sq ft of paintable wall, about 2.4 gallons at two coats, so you'd buy three.
Round up rather than down. A partly-used gallon is worth having for touch-ups; a half-finished wall at 6pm on a Sunday is not.
A quick reference
| Container | One coat | Two coats |
|---|---|---|
| 1 quart | 85 to 100 sq ft | 45 to 50 sq ft |
| 1 gallon | 350 to 400 sq ft | 175 to 200 sq ft |
| 2 gallons | 700 to 800 sq ft | 350 to 400 sq ft |
| 5 gallons | 1,750 to 2,000 sq ft | 875 to 1,000 sq ft |
Working out a whole house instead of a single room? See how much paint you need for room-by-room figures, or whether a 5-gallon bucket is worth it.
Skip the arithmetic
Enter your own dimensions and get the exact figure instead of working from averages.
Open the Paint CalculatorFrequently asked questions
About 350 to 400 square feet in one coat on a smooth, primed surface. Most manufacturers print 400 sq ft on the can; 350 is the more realistic working number once you account for normal application. At two coats, expect roughly 175 to 200 square feet of wall per gallon.
Only under ideal conditions: smooth, primed, previously painted drywall in a similar color, applied by roller at the recommended film thickness. Real rooms rarely hit that. Textured walls, bare drywall, and porous surfaces all pull the number down, sometimes by 30% or more.
A quart is a quarter of a gallon, so roughly 85 to 100 square feet in one coat. That's enough for a small accent area, a door, or trim work, but not a full room.
The three usual culprits are surface texture, surface porosity, and color change. Textured or unprimed surfaces have more actual area to cover and absorb more paint, and a dramatic color change often needs an extra coat regardless of coverage rate.
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