Primer Calculator.
Calculate the exact volume of primer required for raw or previously painted substrates before coloring.
Wall Substrate Details
Recommended buy: 2 cans (1-gallon)
Primer builds a sealing foundation layer, preventing the porous substrate from sucking up expensive color paint.
The Importance of Primer.
Why paint primer is necessary
Primer is not just "watered-down cheap white paint." It is formulated with a higher ratio of binders and sealing solids. Primer provides a consistent adhesive surface for paint to lock onto, seals porous drywall paper, and blocks stains or old darker paint colors from bleeding through your new coat.
Failing to prime raw sheetrock or brick will result in uneven sheen (banding), peeling paint, and requiring 3 to 4 coats of expensive topcoat paint instead of just 1 primer + 2 paint coats.
Porosity presets
Different surfaces absorb liquids differently:
- **New Plaster / Drywall**: Highly porous. It absorbs water instantly and requires a PVA-specific sealer primer.
- **Concrete / Brick**: Extremely porous. The rough texture creates massive surface area. Often requires masonry block-fillers.
- **Previously Painted Walls**: Non-porous. A primer is usually only needed if making a drastic color change (e.g. dark blue to light yellow) or changing chemical types (e.g. putting water-based latex over an old oil-based glossy paint).