About 1.5–2 gallons for two coats. A standard 12×12 bedroom with 8-foot ceilings, one door, and one window has roughly 380 sq ft of paintable wall area. Two coats with a 10% waste allowance lands at about 1.5 gallons — round up to 2 to be safe.

Two coats is the standard recommendation. One coat rarely gives even color, especially over a different base. Use three coats only when going from dark to light, covering stains, or when the manufacturer specifies it for the product you bought.

Yes — up to 40% more. Smooth walls take about 375 sq ft per gallon. Lightly textured walls drop to roughly 325 sq ft, and heavily textured surfaces like stucco or popcorn can drop to 225 sq ft per gallon because the surface has more area to coat.

Yes — add roughly 10% extra. A 10% waste allowance covers spills, roller absorption, and uneven coverage. Keeping a small leftover amount in a sealed container also lets you patch scuffs and nail holes later with an exact match.

Roughly 350–400 sq ft (32.5–37 sq m) on smooth walls. That is enough for a single coat on a small bedroom wall. Coverage drops on textured surfaces, porous primer coats, and dark-over-light situations where extra paint is needed.

Multiply length by width to get ceiling area, then divide by 350. A 12×12 ceiling is 144 sq ft, which needs about half a gallon for two coats. Textured ceilings drop coverage by 20–40%, so plan for closer to a full gallon if the surface is heavy.

Oil-based covers slightly more — about 400 sq ft per gallon vs 375 for latex. Oil-based paint flows further and self-levels, but takes longer to dry and needs solvent cleanup. For most interior walls, latex is the standard and the small coverage difference rarely matters.

Plan on 200–300 sq ft per gallon — about 25% more than your finish paint. Primer is designed to soak into and seal the surface, so coverage is lower. For a standard bedroom, expect to use 1 to 1.5 gallons of primer before your color coats.