How Much Paint for a 12×12 Room? Gallons for 8, 9 and 10 ft Walls
A 12×12 room with 8 ft walls needs about 2 gallons of paint for two coats on the walls, plus about 1 gallon for the ceiling. Here’s the math, and how taller walls change it.
The quick answer
For a 12×12 ft room with 8 ft walls, one standard door and two average windows, there is about 334 ft² of wall to paint. Sherwin-Williams says a gallon typically covers 350–400 ft² per coat. Using the cautious 350 ft²:
- One coat: 334 ÷ 350 = 0.95 gallon, so 1 gallon.
- Two coats: 668 ÷ 350 = 1.91 gallons, so 2 gallons.
- Ceiling, two coats: 144 ft² × 2 ÷ 350 = 0.82 gallon, so 1 gallon of ceiling paint.
Step by step
- Perimeter: 12 + 12 + 12 + 12 = 48 ft.
- Gross wall area: perimeter × wall height = 48 × 8 = 384 ft².
- Subtract openings: a 36 × 80 in door is 20 ft², and 15 ft² is a common allowance for an average window. 384 − 20 − 2 × 15 = 334 ft².
- Multiply by coats and divide by coverage from the label. Round up to whole gallons, or gallons plus quarts.
Taller walls
| Wall height | Gross wall | Paintable (1 door, 2 windows) | 1 coat | 2 coats |
|---|---|---|---|---|
| 8 ft | 384 ft² | 334 ft² | 0.95 gal → 1 gal | 1.91 gal → 2 gal |
| 9 ft | 432 ft² | 382 ft² | 1.09 gal → 1 gal + 1 qt | 2.18 gal → 2 gal + 1 qt |
| 10 ft | 480 ft² | 430 ft² | 1.23 gal → 1 gal + 1 qt | 2.46 gal → 2 gal + 2 qt |
Quarts cost more per ounce than gallons. If the gallon count lands just above a whole number, a third gallon can cost about the same as a gallon plus two quarts, and the leftover is handy for touch-ups.
Metric: a 3.66 × 3.66 m room
A 12×12 ft room is 3.66 m square. With 2.4 m walls the gross wall area is 35.1 m². Subtract a 1.9 m² door and two 1.4 m² windows to get 30.4 m². UK emulsions often list coverage of “up to” 13–14 m² per litre. At a more cautious 10 m²/L, two coats need 6.1 L, which is a 5 L tin plus two 1 L tins, or two 2.5 L tins and a 1 L tin. At the label’s best case (14 m²/L), it would be about 4.3 L. That gap is why it helps to read your actual tin and think about the surface.
When you’ll need more
- Big colour changes. Going from a dark colour to a light one (or the reverse) often needs an extra coat or a primer first; check the paint label’s advice.
- Porous or textured walls. New plaster, bare drywall and textured finishes soak up more paint. Sherwin-Williams says a gallon of primer covers about 200–300 ft².
- Spraying. Overspray uses more paint than rolling.
- Trim and doors. These aren’t in the wall figure. Sherwin-Williams says a quart covers about 100 ft², usually enough for one room’s door and baseboards.
When you’ll need less
- Repainting the same or a similar colour over a sound, previously painted wall. One coat can be enough if the label supports it.
- Rooms with large windows, built-ins or a wall of cabinets. Subtract their area too.
For other room sizes, ceilings and primer, use the paint calculator, which works in gallons or litres.
Frequently asked questions
How much paint do I need for a 12×12 room?
About 2 gallons for two coats on 8 ft walls (334 ft² after one door and two windows, at 350 ft² per gallon), plus about 1 gallon for two coats on the ceiling.
Is one gallon of paint enough for a 12×12 room?
For one coat on 8 ft walls, about 1 gallon covers it. For the usual two coats, you need about 2 gallons.
How much paint for a 12×12 room with 9 ft ceilings?
About 382 ft² of wall after openings. Two coats at 350 ft² per gallon need 2.18 gallons, so buy 2 gallons and 1 quart.
How many litres of paint for a 12×12 room?
About 6 L for two coats on 2.4 m walls at a cautious 10 m² per litre. On smooth walls with a high-coverage emulsion it can be closer to 4.5 L.