Enter the room’s length, width and wall height. You get gallons of wall paint, ceiling paint and primer, each rounded up to whole cans.
Two coats on walls 8 ft high plus the ceiling, at 375 sq ft per gallon per coat.
| Room | Wall paint | Ceiling paint | Total |
|---|---|---|---|
| 10 × 10 ft | 2 gal | 1 gal | 3 gal |
| 12 × 12 ft | 3 gal | 1 gal | 4 gal |
| 12 × 14 ft | 3 gal | 1 gal | 4 gal |
| 14 × 16 ft | 3 gal | 2 gal | 5 gal |
| 16 × 20 ft | 4 gal | 2 gal | 6 gal |
Wall area is the room’s perimeter × wall height; the ceiling is length × width. Each is multiplied by the number of coats, divided by 375 sq ft per gallon, and given 5% extra for cutting in and touch-ups.
Walls and ceiling round up to whole gallons separately, because ceilings usually get their own flat white. Primer covers about 300 sq ft per gallon, one coat over everything.
Doors and windows are not subtracted; for a typical room the openings are about what you keep for touch-ups. These are the same factors as the paint cost calculator.
Sources:
Quantities are for planning and ordering. Check the plan, the supplier’s product data and local code before you buy; for structural concrete, follow the drawings.
A 12 × 12 ft room with 8 ft walls has 384 sq ft of wall and 144 sq ft of ceiling. Two coats take 3 gallons for the walls and 1 for the ceiling, 4 gallons in all.
About 350 to 400 square feet per coat on smooth, primed walls; this tool uses 375. Rough or porous surfaces such as new drywall, textured walls and bare wood drink more, so coverage drops.
Usually not on walls already painted in good condition. Prime new drywall and patches, stains, glossy surfaces, and a big change from dark to light. A gallon of primer covers about 300 square feet.
For one room, not usually. A standard door is about 21 square feet and a window about 15, which is roughly the paint you will want on hand for touch-ups. For a room with a wall of windows, subtract them and the count drops.
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