Wall paint for an 18×20 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 | 557 sq ft | 3.18 gal | 3 gallons + 1 quart |
| 9 ft | 633 sq ft | 3.62 gal | 4 gallons |
| 10 ft | 709 sq ft | 4.05 gal | 4 gallons + 1 quart |
Ceiling paint
The ceiling is 360 sq ft. One coat needs 1 gallon + 1 quart; two coats need 2 gallons + 1 quart. Flat ceiling paint hides imperfections best.
Buying for this room
Walls and ceiling together come to about 5.2 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 2 gallons for the walls.
The math
Common questions
How many gallons of paint for an 18x20 room?
3 gallons + 1 quart for two coats on the walls with 8 ft ceilings, plus 2 gallons + 1 quart if you paint the ceiling.
How much paint for an 18x20 room with 9 ft ceilings?
4 gallons for two coats on the walls.
Is one gallon enough for an 18x20 room?
No — even one coat on the walls takes 1.59 gallons.
Want the full method, tips and other sizes? See the paint calculator guide.