calcs.homes
calcs.homes
Enter the area to prime, the number of coats, and what you are priming over, and this primer calculator estimates the gallons to buy.
Estimate only — bare, porous, and patched surfaces soak up primer faster than the label rate.
Primer coverage depends on what it is soaking into. On a previously painted wall it spreads like paint, around 350 sq ft per gallon. On bare drywall or new joint compound it drops to about 200, because the porous face and paper drink the first coat. We multiply your area by the number of coats and divide by the rate for the surface you picked.
One coat of primer is normally enough; a second is worth it over deep patch repairs, glossy old paint that was only scuffed, or a drastic color change. For stains — water marks, smoke, tannin bleed from knots — use a dedicated stain-blocking primer and spot-prime those areas rather than a whole extra coat everywhere.
One is usually enough. Add a second coat only over heavy patching, slick old gloss, or when going from a very dark color to a light one.
About 350 sq ft on an already-painted wall, but only 200–250 sq ft on bare drywall, new mud, or raw wood that absorbs the first coat.
Over a sound, similar-color painted wall, often yes. Over bare drywall, big repairs, stains, or a bold color change, a dedicated primer still performs better.