Use the label on your selected primer to adjust coverage for bare, repaired, stained, or previously painted surfaces.
01 / Formula
How this is calculated
Primer = ((surface area − openings) × coats) ÷ coverage02 / Assumptions
What the estimate assumes
- ✓Coverage depends strongly on surface porosity.
- ✓Spot-priming is best measured as its own area.
- ✓This estimates quantity, not whether a specific primer is compatible with the substrate.
03 / Worked example
See the math in context
For 700 sq ft of net surface, one coat at 300 sq ft/gal requires 2.33 gallons; three gallons is a practical purchase.
04 / Guidance
When the estimate can change
New drywall, raw wood, patched areas, stains, and strong color changes can absorb or require more primer. Follow coating compatibility and recoat instructions from the manufacturer.
Questions
Frequently asked
Should I round up when buying paint?+
Yes. Paint is sold in fixed container sizes, and a small reserve helps with touch-ups, porous surfaces, and application loss. The calculator shows both the theoretical quantity and a practical purchase amount.
Does paint coverage include two coats?+
Coverage printed on a can is normally stated per coat. Two coats cover the same surface twice, so the calculator multiplies net area by the number of coats before dividing by the selected coverage rate.