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Calculate how much primer you need based on surface area, surface type, and number of coats with industry-standard coverage rates.
Calculate the total wall or ceiling area to be primed. For walls, multiply wall height by perimeter length. Subtract window and door areas if significant. For ceilings, multiply length by width.
Choose the surface material: new drywall, bare wood, masonry/concrete, or previously painted. Each surface has a different absorption rate that affects how much primer you need per square foot. The calculator uses industry-standard coverage rates for each surface type.
One coat is standard for most applications. Select 2 coats for porous surfaces or dramatic color changes. The waste factor (default 10%) accounts for roller absorption, overlap, and touch-up. Spray application may have higher waste.
The calculator divides total area (times coats) by the surface-specific coverage rate, adds the waste factor, and rounds up. Results show gallons needed and equivalent quarts for smaller purchases at paint counters.
Primer is sold in quarts and gallons. Buy gallons for large areas (more cost effective) and quarts for touch-ups or small rooms. Unopened cans are usually returnable, so it is better to have a little extra than to run short mid-project.
“Paint and primer in one” products work best on previously painted surfaces in good condition. For new drywall, bare wood, or masonry, a dedicated primer provides better adhesion and sealing. Using the right primer can actually save you money by reducing the number of topcoats needed for full coverage.
Total wall or ceiling area to prime
PVA or drywall primer
1 coat is standard; 2 for porous surfaces or color change
Recommended: 10% for roller/brush application
New Drywall @ 350 sq ft/gal
For smaller quantities at paint counters
1 coat
sq ft per gallon