Paint for a 9 × 12 ft room
This is a guest bedroom or a small dining room. With 8 ft ceilings the four walls have 336 ft² of surface, and after deducting one door (21 ft²) and two windows (30 ft²) there are 285 ft² to paint. The ceiling is 108 ft².
How the number of coats changes it
| Coats | Wall gallons | Buy for walls | Ceiling gallons | Buy for ceiling |
|---|---|---|---|---|
| 1 coat | 0.81 | 1 gallon | 0.31 | 2 quarts |
| 2 coats | 1.63 | 1 gallon + 3 quarts | 0.62 | 3 quarts |
| 3 coats | 2.44 | 2 gallons + 2 quarts | 0.93 | 1 gallon |
If your ceilings are taller
| Ceiling height | Wall area | Gallons (2 coats) | Buy |
|---|---|---|---|
| 8 ft ceilings | 336 ft² | 1.63 | 1 gallon + 3 quarts |
| 9 ft ceilings | 378 ft² | 1.87 | 2 gallons |
| 10 ft ceilings | 420 ft² | 2.11 | 2 gallons + 1 quart |
If your walls are rough or your paint covers less
The label on your can gives its coverage. Rough or textured walls and dark colors cover less, so the amounts go up:
| Coverage | Gallons (2 coats) | Buy |
|---|---|---|
| 250 ft² per gallon | 2.28 | 2 gallons + 2 quarts |
| 300 ft² per gallon | 1.90 | 2 gallons |
| 350 ft² per gallon | 1.63 | 1 gallon + 3 quarts |
| 400 ft² per gallon | 1.43 | 1 gallon + 2 quarts |
Trim, tape and prep
The room is 42 ft around. Taping both the ceiling line and the baseboard is 84 ft of painter's tape, which is 1 roll of 60 yard tape. A quart of trim paint usually covers the baseboards and window and door casings for a room this size, and a gallon of primer is worth having for stains and patches.
Paint one wall at a time from the ceiling down, "cut in" the edges with a brush before rolling, and keep a wet edge to avoid lap marks. Let the first coat dry fully before the second, as the can directs.
A 9 × 12 room: a guest room you can finish in a weekend
In a 9 × 12 ft room the four walls come to 285 sq ft once the door and windows are deducted, and the ceiling is 108 sq ft. Two coats on the walls take 1.63 gallons (1 gallon + 3 quarts), and two on the ceiling take 0.62 gallons.
Walls and ceiling together are 2.25 gallons, so a guest room is a small enough order to do properly: wash the walls, fill the nail holes from old pictures and spot-prime the filler before the first coat. The two 12 ft walls are the ones you see from the door, so roll those last, in one pass from corner to corner, when your technique has warmed up.
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Tools & materials for this project
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Frequently asked questions
How many gallons of paint do I need for a 9x12 room?
With 8 ft ceilings, one door, two windows and two coats at 350 ft² per gallon, the walls need 1.63 gallons, so buy 1 gallon + 3 quarts. If you also paint the ceiling, add 0.62 gallons (3 quarts).
How much paint for the walls and ceiling of a 9x12 room?
Walls and ceiling together need about 2.25 gallons for two coats. That is 2 gallons + 1 quart if you use the same paint on both, though ceilings are usually painted with a separate flat ceiling paint.
How much primer do I need for a 9x12 room?
One coat of primer over the same walls is about 0.81 gallons (1 gallon). Primer often covers a little less than paint on bare surfaces, so check the can.
Related sizes and guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.