How much paint for a 12x12 room?
A 12 by 12 foot room with 8 foot ceilings needs about 2.2 gallons of paint for two coats, so buy 3 gallons. That allows for one door, one window, and a 10 percent waste factor, at a coverage rate of 350 square feet per gallon.
If your paint is rated at 400 square feet per gallon, the same room needs 1.92 gallons, and 2 gallons is enough.
The full arithmetic
| Wall perimeter | (12 + 12) × 2 = 48 ft |
| Gross wall area at 8 ft | 48 × 8 = 384 sq ft |
| Subtract one door | -20 sq ft |
| Subtract one window | -15 sq ft |
| Net wall area | 349 sq ft |
| Two coats | 698 sq ft |
| Plus 10 percent waste | 767.8 sq ft |
| Divided by 350 sq ft per gallon | 2.19 gallons, buy 3 |
Ceiling height changes the answer
Wall area scales directly with ceiling height, so a 10 foot ceiling is 25 percent more wall than an 8 foot one. Same room, same door and window, two coats, 10 percent waste, 350 square feet per gallon:
| Ceiling height | Net wall area | Two coats with waste | Gallons | Buy |
|---|---|---|---|---|
| 8 ft | 349 sq ft | 767.8 sq ft | 2.19 | 3 gallons |
| 9 ft | 397 sq ft | 873.4 sq ft | 2.50 | 3 gallons |
| 10 ft | 445 sq ft | 979.0 sq ft | 2.80 | 3 gallons |
All three land on 3 gallons, which is a useful thing to know before you measure your ceiling precisely. The height only changes the purchase once you go past about 10.5 feet.
Adding the ceiling
A ceiling has the same area as the floor, so a 12 by 12 room has a 144 square foot ceiling. One coat with 10 percent waste is 158.4 square feet, which is 0.45 of a gallon at 350 square feet per gallon. Buy 2 quarts, or a full gallon if you plan to paint other ceilings in the same color.
Ceiling paint is usually a separate flat white product rather than your wall color, so it is a separate purchase either way. Two coats on the ceiling brings it to 316.8 square feet, or 0.9 gallons, at which point a single gallon is the sensible buy.
What would change this estimate
- More windows. Each additional standard window takes roughly 15 square feet off the total, which is small. Three large windows might save you a quarter gallon.
- Textured walls. Knockdown or orange peel drops your coverage rate. See paint coverage by surface type for the right rate to use.
- A dark to light color change. Budget for a third coat, which takes this room to about 3.3 gallons and a 4 gallon purchase.
- Bare or patched drywall. Prime first. Unprimed drywall can cut your coverage to 250 square feet per gallon or less.
To change any of these assumptions, including door and window counts, coats, and waste, use the paint calculator.
Frequently asked questions
How many gallons of paint for a 12x12 room?
About 2.2 gallons for two coats on the walls, so you buy 3 gallons. For a single coat it is 1.1 gallons, so 2 gallons covers it with paint left over.
How much paint for a 12x12 room with the ceiling included?
Add about half a gallon for one ceiling coat, or a full gallon for two. The ceiling is 144 square feet, the same as the floor area. Ceiling paint is normally a separate flat white product, so buy it separately from the wall color.
Is one gallon enough for a 12x12 room?
For one coat on a small part of the room, yes, but not for the whole room. A single gallon covers 350 to 400 square feet and the room has 349 square feet of net wall, so one gallon just barely does one coat with nothing spare. For two coats you need three.
How much does it cost to paint a 12x12 room?
Three gallons of mid-range interior paint is the main cost, plus roller covers, a tray, painter's tape, and drop cloths. Prices vary widely by brand and region, so price the three gallons at your local store and add roughly the cost of one more gallon for materials.
How long does it take to paint a 12x12 room?
For one person, plan a full day for two coats including cutting in around the ceiling, trim, and outlets, plus the drying time between coats. The painting itself is quicker than the preparation, which is where most of the time goes.