How it's worked out
- Wall area: 2 × (15 + 20) × 8 ft = 560 sq ft
- Minus openings: 21 sq ft for the door and 15 sq ft for each window = 509 sq ft
- Two coats: 509 × 2 = 1,018 sq ft
- Gallons: 1,018 ÷ 350 sq ft per gallon = 2.91 gal
15x20 room: other ceiling heights
| Walls | Wall area | Paint for 2 coats | Buy |
|---|---|---|---|
| 8 ft | 509 sq ft | 2.9 gal | 3 gal |
| 9 ft | 579 sq ft | 3.3 gal | 3 gal + 2 qt |
| 10 ft | 649 sq ft | 3.7 gal | 4 gal |
The ceiling is 300 sq ft and takes 1.7 gallons for two coats. Use ceiling paint, which is flatter and spatters less.
Coverage of 350 sq ft per gallon is typical for smooth, previously painted walls. Textured walls, fresh drywall and big color changes use more, so check the label on your can and change the coverage in the calculator.
Other common sizes
- 10 × 10 ft room
- 10 × 12 ft room
- 12 × 12 ft room
- 12 × 14 ft room
- 12 × 15 ft room
- 14 × 16 ft room
- 15 × 20 ft room
- 20 × 20 ft room
More detail: How Much Paint Do I Need for a Room? A Simple Guide