Paint Coverage Calculator Guide
Understanding Paint Coverage
Calculating paint seems simple—measure the walls and buy the paint—but professional results require a bit more math. The "spread rate" of paint varies by brand and surface texture, and failing to account for multiple coats is the most common DIY mistake.
The Golden Rule: 350-400 Sq Ft
A standard gallon of high-quality interior latex paint typically covers 350 to 400 square feet with a single coat.
Total Area = (Wall Width × Wall Height) - (Window/Door Areas)
Gallons Needed = (Total Area / 350) × Number of Coats
Always round up to the nearest quart or gallon. It's better to have leftover paint for touch-ups than to run out mid-wall, which can lead to visible "lap marks" when you restart.
Surface Texture Matters
Smooth Surfaces
New drywall (primed), previously painted walls, or smooth siding.
- Coverage: ~400 sq ft per gallon
- Absorption: Low
Rough/Textured Surfaces
Stucco, brick, raw wood, or heavy texture (popcorn ceilings).
- Coverage: ~250-300 sq ft per gallon
- Absorption: High (requires more paint!)