Paint for a 12 × 18 ft room with 9 ft ceilings on a textured wall, 2 coats
| Paint | 3.43gal |
|---|---|
| What to buybuckets only pay from about 3.6 gal | 4 × 1 gal |
| Wall area540 ft² less 1 door and 1 window | 504ft² |
| Spread rateorange peel or knockdown adds surface area | 275ft²/gal |
| First coat | 1.83gal |
| Each later coat14.999999999999991% further — the surface is sealed now | 1.59gal |
| Doubling the first coat would say0.24 gal more than you need | 3.67gal |
| Masking tape91 ft of edge | 260 yd rolls |
- Room length
- 12 ft
- Room width
- 18 ft
- Ceiling height
- 9 ft
- Surface
- a textured wall
- Coats
- 2
- Doors
- 1
What to buy
3.43 gallons — 4 × 1 gal.
504 ft² of wall after openings, at 275 ft² per gallon on a textured wall.
Spread rate belongs to the surface, not the tin
The "400 square feet per gallon" printed on a can is measured on smooth primed drywall. a textured wall takes about 275, and that difference is the single biggest reason people run out.
Rough and porous surfaces are worst: stucco can halve the figure on the label.
The second coat is cheaper than the first
Once the surface is sealed, paint spreads about 15% further. 2 coats here comes to 3.43 gallons — not 3.67, which is what doubling the first coat would say.
That difference is 0.24 gallons of paint that would sit in the garage until it went off.
Box it before you start
Pour every tin into one bucket and mix. Tins of the same color from different batches differ slightly, and a wall painted from two tins shows the join exactly where you stopped for lunch.
Trim does not scale with the room
Doors, trim and ceilings are linear-foot work and a completely separate calculation. A room needing 3.43 gallons of wall paint typically takes under a quart of trim enamel.
Cutting in is the job
91 ft of edge here — that is where the hours go, not the rolling. A good 2½″ angled sash brush beats tape on most edges; tape earns its place mainly against carpet and glass.
Notes
- **Spread rate is a property of the surface, not the paint.** Textured wall takes about 275 ft² per gallon — orange peel or knockdown adds surface area. The "400 square feet" on the tin is measured on smooth primed drywall, which is the best case and rarely the case.
- **The second coat is cheaper than the first.** Once the surface is sealed, paint spreads about 14.999999999999991% further. 2 coats here is 3.43 gal, not 3.67 — doubling the first coat over-buys by 0.24 gal, which at retail is real money left in the garage.
- Buy all of it in one go and box it — pour every tin into one bucket and mix. Tins of the same colour from different batches differ slightly, and a wall painted from two tins shows the change where they met.
- Trim, doors and ceilings do not scale with floor area — they scale with linear feet, and they are a separate calculation. A room that takes 3.43 gal of wall paint typically takes under a quart for the trim.
- Cutting in is where the time goes, not rolling. 91 ft of edge here. A decent 2½″ angled sash brush and a steady hand beat tape on most edges, and tape is worth it mainly against carpet and glass.
Nearby sizes
- Paint for a 11 × 18 ft room with 9 ft ceilings on a textured wall, 2 coats
- Paint for a 13 × 18 ft room with 9 ft ceilings on a textured wall, 2 coats
- Paint for a 10 × 18 ft room with 9 ft ceilings on a textured wall, 2 coats
- Paint for a 14 × 18 ft room with 9 ft ceilings on a textured wall, 2 coats
- Paint for a 12 × 16 ft room with 9 ft ceilings on a textured wall, 2 coats
- Paint for a 12 × 14 ft room with 9 ft ceilings on a textured wall, 2 coats
- Paint for a 12 × 18 ft room with 8 ft ceilings on a textured wall, 2 coats
- Paint for a 12 × 18 ft room with 10 ft ceilings on a textured wall, 2 coats
- Paint for a 12 × 18 ft room with 9 ft ceilings on new drywall, 2 coats
- Paint for a 12 × 18 ft room with 9 ft ceilings on wood siding, 2 coats
- Paint for a 12 × 18 ft room with 9 ft ceilings on primed drywall, 2 coats
- Paint for a 12 × 18 ft room with 9 ft ceilings on stucco, 2 coats
- Paint for a 12 × 18 ft room with 9 ft ceilings on a textured wall, 1 coats
- Paint for a 12 × 18 ft room with 9 ft ceilings on a textured wall, 3 coats
- Paint for a 12 × 18 ft room with 9 ft ceilings on a textured wall, 2 coats
Read more
- Cost to Paint a House Interior per Square Foot: Two Numbers, Not OneContractors quote per square foot of floor and work per square foot of wall. Knowing which number a bid uses is the difference between comparing quotes and guessing.
- Painter Cost per Hour or per Room: Who Carries the RiskA fixed price is not a better deal or a worse one. It is a transfer of risk, and which direction you want that to go depends on how well you can see the prep.
- Does the Second Coat Use Less Paint? Usually, and by Less Than You ThinkOn new drywall the second coat uses a quarter less. On a previously painted wall it uses the same. The variable is how much the substrate is drinking.
- What Painters Charge to Paint a Ceiling, and Why It Costs More Than a WallA ceiling is the same square footage as a floor and costs 30 to 60 percent more than a wall to paint. Height, gravity and light are all working against it.