How Much Paint Do You Need for a Room? The Quick Formula (Plus Mistakes to Avoid)
Buy too little and you make a second trip mid-project with half-dried walls. Buy too much and you store three unused gallons for a decade. Here is how to get it right.
The rule of thumb — one gallon per 350 square feet — gets you close but not precise. A standard 12×14 bedroom with 8-foot ceilings has about 416 square feet of wall area. Subtract two windows (30 sq ft) and a door (21 sq ft), and you have 365 paintable square feet. One coat needs just over one gallon. Two coats needs just over two gallons. Buy three gallons: two for the walls and one for the ceiling (which is roughly 168 sq ft in this room).
The Mistakes That Cost You
Mistake one: forgetting the second coat. Almost every paint job requires two coats. The first coat looks fine when wet but shows streaks, thin spots, and the old color bleeding through once it dries. The second coat is what makes it look professional. Budget for two coats from the start.
Mistake two: not accounting for texture. Smooth drywall absorbs less paint — you get the full 350 sq ft per gallon. Textured walls (knockdown, orange peel, stucco) have more surface area and absorb more paint, reducing coverage to 250-300 sq ft per gallon. If your walls are textured, increase your estimate by 20-30%.
Mistake three: ignoring color changes. Painting a dark color over a light one requires primer plus two coats. Painting light over dark requires a tinted primer plus two coats. Skipping primer means three or four coats of expensive finish paint — primer at $15-20 per gallon saves money compared to extra coats of $40-70 finish paint.
The Money-Saving Move
Most paint stores will color-match any sample you bring in. Instead of buying expensive designer paints, find the color you like at any store, get a sample chip, and bring it to a store that sells quality paint at lower prices. Behr (Home Depot) and Valspar (Lowes) both offer professional-grade formulas at 40-50% less than Benjamin Moore or Sherwin-Williams, and their color matching is accurate to within a shade that human eyes cannot distinguish.
Get the exact calculation for any room with our paint calculator — enter dimensions, doors, windows, and coats for a precise gallon count with cost estimate.