Wall paint for a 15×20 room by ceiling height
Two coats, 350 sq ft per gallon, one door and two windows subtracted.
| Ceiling height | Wall area | Exact paint | Buy |
|---|---|---|---|
| 8 ft | 509 sq ft | 2.91 gal | 3 gallons |
| 9 ft | 579 sq ft | 3.31 gal | 3 gallons + 2 quarts |
| 10 ft | 649 sq ft | 3.71 gal | 4 gallons |
Ceiling paint
The ceiling is 300 sq ft. One coat needs 1 gallon; two coats need 2 gallons. Flat ceiling paint hides imperfections best.
Buying for this room
Walls and ceiling together come to about 4.6 gallons. At this amount, compare the price of a 5-gallon bucket against single gallons — the bucket is often cheaper and keeps the tint identical. Need primer for new drywall or a big color change? Plan on 1 gallon + 2 quarts for the walls.
The math
2 × (15 + 20) × 8 ft = 560 sq ft
− 1 door (21) − 2 windows (30) = 509 sq ft
509 × 2 coats ÷ 350 = 2.91 gallons
Common questions
How many gallons of paint for a 15x20 room?
3 gallons for two coats on the walls with 8 ft ceilings, plus 2 gallons if you paint the ceiling.
How much paint for a 15x20 room with 9 ft ceilings?
3 gallons + 2 quarts for two coats on the walls.
Is one gallon enough for a 15x20 room?
No — even one coat on the walls takes 1.45 gallons.
Want the full method, tips and other sizes? See the paint calculator guide.