15×20 room: paint by wall height
| Wall height | Paintable sq ft | Gallons (2 coats) | Buy |
|---|---|---|---|
| 8 ft | 510 | 2.91 | 3 |
| 9 ft | 580 | 3.31 | 4 |
| 10 ft | 650 | 3.71 | 4 |
1 door and 2 windows deducted; 350 sq ft per gallon.
Worked example
Perimeter: 2 × (15 + 20) = 70 ft. With 8 ft walls: 560 sq ft, minus 20 (door) and 30 (two windows) = 510 sq ft. Two coats: 1020 ÷ 350 = 2.91 gallons. The ceiling adds 300 sq ft per coat (about 1.71 gallons for two coats).
Frequently asked questions
How many gallons to paint a 15×20 room?
About 2.91 gallons for two coats on 8 ft walls (buy 3).