Primer Calculator
How many gallons of primer you need
Priming before you paint? Enter your wall dimensions to find how many gallons of primer to buy.
How much primer?
Primer covers a bit less than paint — about 250–300 ft² per gallon — because it soaks into porous surfaces. One coat of primer is usually enough over clean drywall or for color changes.
When primer is worth it
Prime new drywall (raw paper and joint compound absorb paint unevenly), bare wood, patches and repairs, glossy surfaces that need a bond coat, and stains like water marks, smoke or marker that bleed through. A stain-blocking or shellac-based primer seals problem spots that ordinary paint can't hide.
Primer vs. paint-and-primer-in-one
"Paint and primer in one" is really a thicker self-priming paint — fine over a sound, similar-colored wall, but no substitute for a dedicated primer on new, bare or stained surfaces. When in doubt, a separate primer coat gives better adhesion and truer color in fewer finish coats.
Primer Calculator: frequently asked questions
Do I need primer before painting?
Yes for new drywall, bare wood, stains, or big color changes. Over a sound, similar-color wall you can often skip it.
How much does primer cover?
About 250–300 square feet per gallon, less than finish paint.
Can I tint primer to match my paint?
Yes — having the store tint your primer toward the finish color, especially for deep or bold shades, helps the topcoat cover in fewer coats and look richer. Most primers accept a partial dose of colorant.