Primer Calculator

Multiply the surface area by the number of coats, add your waste factor (10% is standard), then divide by the coverage rate for your surface. For example: 1,000 sq ft × 1 coat × 1.10 ÷ 350 sq ft/gal = 3.2 gallons of drywall primer. Our primer calculator does this automatically and converts the result into the exact cans and pails you should buy.

With new drywall at 350 sq ft per gallon, one coat and a 10% waste factor, 1,000 sq ft needs about 3.2 gallons — so buy three 1-gallon cans plus one 1-quart can. On previously painted surfaces (400 sq ft/gal) the same area needs roughly 2.8 gallons, while bare masonry at 200 sq ft/gal can take up to 5.5 gallons.

A 10 ft × 10 ft room with 8 ft ceilings has 320 sq ft of wall. Subtract one standard door (21 sq ft) and one standard window (15 sq ft) and you prime about 284 sq ft. At 350 sq ft/gal with 10% waste that is just under 0.9 gallons — one 1-gallon can covers it with touch-up left over. Add the ceiling (100 sq ft) and you are at about 1.2 gallons.

Most PVA drywall primers cover 300–400 sq ft per gallon, with 350 sq ft/gal the industry-standard planning number. Bare, porous first coats sit at the low end; a second skim-coated pass reaches the high end. Bare wood (≈250 sq ft/gal) and masonry (≈200 sq ft/gal) absorb far more.

One coat is standard for new drywall and sound surfaces. Use two coats when transitioning from a dark to a light color, sealing stains, odors or smoke damage, or priming high-porosity bare surfaces like wood and masonry. Two thin coats always outperform one heavy coat because each layer can do its sealing job properly.

Expect roughly one gallon of primer per 200–400 sq ft depending on the surface: about 0.0029 gal/sq ft on new drywall, 0.004 gal/sq ft on bare wood, and 0.005 gal/sq ft on masonry. Multiply your square footage by the surface-specific number, then add 10% waste.

Buy 5-gallon pails for jobs over about 10 gallons, 1-gallon cans for typical rooms and accents, and quarts for small patches, doors and trim. Our calculator's Auto package mode fills large pails first, then 1-gallon cans, then rounds the remainder up to whole quarts — so you never stand at the counter wondering what to ask for.

Multiply the primer volume by the shelf price per gallon. Most interior primers run $15–$40 per gallon: budget PVA around $15–$20, all-purpose around $25–$30, and premium stain-blocking or shellac primers $35–$50. Enter your local price in the calculator and it shows both the true material cost and what you will actually pay for the rounded-up can mix.

Yes. Primer is formulated to soak in and seal, so its coverage is usually a bit lower than finish paint, especially on porous first-time surfaces. Plan projects with the surface-specific primer rates in this calculator rather than the coverage printed on your topcoat can.

With 8 ft ceilings, a 12 × 12 room has 384 sq ft of wall; subtract one door and one window and you prime about 348 sq ft. At 350 sq ft/gal with 10% waste that is 1.1 gallons — one 1-gallon can plus one quart. Add the 144 sq ft ceiling and the job grows to roughly 1.6 gallons, so buy two 1-gallon cans.

Water-based and PVA primers are dry to the touch in 30–60 minutes and ready to recoat in about 3 hours. Oil-based primers need 6–8 hours to touch and a full 24 hours before the topcoat. Shellac primers are fastest — touchable in about 45 minutes and recoatable in 2 hours. Cold or humid rooms stretch every one of these windows.

Yes, and you should for deep colors. Most paint counters will tint a white or light-gray primer halfway toward your topcoat for a few dollars. A tinted base dramatically improves hiding on dark reds, blues and greens, often saving a full finish coat — which costs far more than the tint.

Not always, but it makes good results great. Once the primer is fully dry, a light pass with 220-grit sandpaper (or a sanding sponge) knocks down texture, dust nibs and raised wood grain, and leaves a silk-smooth base for the topcoat. Wipe the dust off with a damp cloth, then paint.

The finish coat soaks in unevenly: joint compound flashes as dull patches while the paper facing stays glossy, so every seam and patch shows through. You also end up applying more topcoats to even it out, which usually costs more than the primer would have. A PVA primer costs a fraction of the fix.

Yes. Orange-peel, knockdown and sand-textured surfaces have significantly more actual area than a flat wall of the same footprint, and the peaks soak up the first coat. Plan on 10–20% more material than the smooth-wall number — or use the lower end of the coverage range for the surface type.

Estimate small surfaces by their area, not their length alone: a standard interior door is about 21 sq ft per side, and trim area is linear feet × trim height in feet (or linear feet × inches ÷ 144). At roughly 400 sq ft/gal on smooth painted surfaces, a single quart covers a door with its frame or about 250–300 linear feet of 4-inch baseboard.

Only on sound, previously painted surfaces, and only with a self-priming paint — and even then two thin topcoats usually beat one heavy one on bare spots. Regular finish paint is not formulated to seal: on new drywall, bare wood, masonry or stains it soaks in unevenly and lets the problem bleed back through. A dedicated primer is always the safer call at those problem areas.

Yes — the same numbers work for any KILZ product. Most KILZ primers, from PVA drywall and all-purpose to premium and oil-based stain-blockers, list practical coverage of roughly 300–400 sq ft per gallon, while specialty masonry and restoration formulas run lower. In the calculator, choose the surface type that matches the KILZ can you are holding, and the gallons, coats, can mix and cost estimates apply directly to that product.

Switch to Direct Area, type your square footage, and the calculator converts square feet to gallons instantly: area × coats × waste factor ÷ the surface's coverage rate. For example, 600 sq ft of new drywall at 350 sq ft/gal with one coat and 10% waste needs about 1.9 gallons — two 1-gallon cans. If you have not measured yet, the room-dimensions mode builds the square footage for you from length, width and height.

Yes, and the difference matters. Finish paint mostly sits on the surface; primer soaks in and seals it, so primer coverage (about 200–400 sq ft per gallon depending on the surface) runs lower than topcoat coverage. This primer paint calculator also adds coat logic for stain-blocking, odor sealing and dark-to-light color changes that a generic paint calculator ignores — using paint numbers for primer leaves you half a gallon short on a mid-size room.