How Much Paint Do I Need for a 12x12 Room?
A 12 × 12 foot bedroom with standard 8-foot ceilings has about 384 square feet of wall. After subtracting roughly 15% for doors and windows, you are left with about 326 square feet to paint — and since one gallon covers around 350 square feet per coat, a single gallon handles one coat. Plan on 2 gallons for the two coats most rooms need, as the chart and worked example below show.
Key Takeaways
- A 12 × 12 ft room with 8 ft ceilings has about 384 sq ft of wall area.
- Subtracting roughly 15% for doors and windows leaves about 326 sq ft to paint.
- One gallon covers about 350 sq ft per coat — so 1 gallon covers a single coat.
- Two coats need 2 gallons; most colors require two coats for even coverage.
- Ceiling paint is separate: a 12 × 12 ceiling adds 144 sq ft (about 1 gallon for two coats).
How to Calculate Paint for a 12x12 Room
Paint math starts with wall area, not floor area. Measure the perimeter, multiply by ceiling height, subtract openings, then divide by coverage per gallon.
- 1Find the perimeter: 12 + 12 + 12 + 12 = 48 linear feet of wall.
- 2Multiply by ceiling height: 48 × 8 = 384 sq ft of wall area.
- 3Subtract doors and windows (about 15%): 384 × 0.85 ≈ 326 sq ft of paintable area.
- 4Divide by coverage: 326 ÷ 350 ≈ 0.93 → round up to 1 gallon per coat.
- 5Multiply by the number of coats: 2 coats = 2 gallons.
The Paint Coverage Formula
Most interior wall paint covers 350–400 square feet per gallon per coat on smooth, primed drywall. Use 350 for the estimate — textured walls and bold color changes need more.
Gallons = (Wall area × Coats) ÷ 350Worked Example: 12 ft × 12 ft Room, 8 ft Ceilings
Full math for the classic 12 × 12 bedroom, plus a chart for other common room sizes (all assume 8 ft ceilings and 15% deducted for openings).
Room dimensions: 12 ft × 12 ft, 8 ft ceilings.
Perimeter: 2 × (12 + 12) = 48 ft.
Wall area: 48 × 8 = 384 sq ft.
Paintable area: 384 × 0.85 ≈ 326 sq ft.
One coat: 326 ÷ 350 = 0.93 → 1 gallon.
Two coats: 0.93 × 2 = 1.86 → 2 gallons.
| Room size | Paintable wall area | 1 coat | 2 coats |
|---|---|---|---|
| 10 × 10 ft | 272 sq ft | 1 gallon | 2 gallons |
| 12 × 12 ft | 326 sq ft | 1 gallon | 2 gallons |
| 15 × 15 ft | 408 sq ft | 2 gallons | 3 gallons |
Common Mistakes
- Using the floor area (144 sq ft) instead of the wall area — paint covers walls, not floors.
- Forgetting to subtract doors and windows, which overstates the paint needed.
- Budgeting for a single coat — most colors need two for uniform coverage.
- Skipping the ceiling or trim, which need their own paint and finish.
- Buying the exact calculated amount with nothing left for touch-ups.
Practical Tips
- Round up, not down — leftover paint is priceless for future touch-ups.
- Two thinner coats look better and last longer than one thick coat.
- Prime first when painting over dark colors or new drywall to improve coverage.
- Buy all gallons for a room at once so the color batch matches.
- Use the NOVORY Paint Calculator to check any room size in seconds.
Calculate Your Paint
Skip the manual math — let the calculator handle it instantly.
Calculate Your Paint