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How many gallons for the job? Enter your room, pick your finish, and get a full paint and supply list — no guesswork, no extra trips.
By BuildCrunch Team · Last updated July 17, 2026
A 14×12 ft room with 8 ft ceilings (1 door, 2 windows, 2 coats, eggshell) needs 2 gallons of paint and 2 gallons of primer — about $136 in materials.
We calculate total wall area (and ceiling, if included), subtract door/window deductions, then multiply by your number of coats to get total coverage needed.
Gallons = coverage ÷ your finish's real-world coverage rate (300-400 sq ft/gallon depending on sheen — lower than the can's claim, to account for texture and technique).
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A standard 12×12 room with 8-foot ceilings has about 384 sq ft of wall space. After deducting a door and two windows, you're looking at roughly 340 sq ft. With two coats, you'll need about 2 gallons of paint plus 1 gallon of primer if you're priming.
Generally yes. Premium paints ($45-$65/gallon) have higher pigment concentration, which means better coverage in fewer coats, better color accuracy, and longer life. A $35 paint that needs 3 coats costs more than a $55 paint that covers in 2 — and takes twice as long to apply.
Latex paint typically needs 2-4 hours between coats. Check the can for the manufacturer's recoat time. Humidity and temperature affect dry time — high humidity or temps below 50°F can double it. The paint should feel dry and smooth to the touch, not tacky.
A quality interior paint job lasts 5-10 years in living areas and 3-5 years in high-traffic zones like hallways and kitchens. Proper prep and primer extend paint life significantly. An unopened can of latex paint lasts up to 10 years stored indoors.
Yes — lightly sand glossy or semi-gloss surfaces with 120-150 grit sandpaper so new paint has something to grip, then wipe down with a damp cloth to remove dust. Fill nail holes and cracks with spackle, sand smooth, and spot-prime bare patches. Skipping prep is the #1 reason paint peels or shows brush marks within a year.
It's possible but not recommended — seams and texture telegraph through, and moisture from the paint can loosen old adhesive, causing bubbling later. If the wallpaper is well-adhered and you're in a hurry, prime with an oil-based or shellac-based primer first. For a lasting result, removing the wallpaper and skim-coating the wall is worth the extra time.