How much paint a room takes
- Wall area is the distance around the room times the ceiling height: 2 × (14 + 12) × 8 = 416 sq ft for a 14 by 12 foot room with 8 foot ceilings.
- Doors and windows come off at 20 sq ft a door and 15 sq ft a window, leaving 366 sq ft to paint.
- Gallons are that area times the coats, divided by the coverage on the can: 366 × 2 ÷ 350 = 2.09 gallons, so 3 gallons.
- The ceiling is the room's length times its width, usually in a flat ceiling paint bought on its own.
What a gallon covers
The label gives the coverage. Most interior paints say 350 to 400 sq ft a gallon on smooth, primed walls, which is why the calculator starts at 350. New drywall, bare plaster, heavy texture and masonry soak up more and cover less, and new drywall takes a coat of primer first. A five-gallon pail at that rate covers about 1,750 to 2,000 sq ft in one coat.
How many coats
Two coats give an even finish and are the usual count for a repaint. One coat can do when the color stays the same and the old paint is sound. A big change in color, dark to light especially, takes primer and two coats.
Common questions
How much paint does a 12 by 12 room take?
With 8 foot ceilings, one door, two windows and two coats: 1.9 gallons for the walls, so 2 gallons, and 1 gallon for the ceiling.
How many square feet does a gallon of paint cover?
About 350 to 400 sq ft in one coat on smooth, primed walls, by most labels. Rough surfaces and spraying change it; the can gives the figure for that paint.
Is trim included?
No. Trim and doors are usually painted in a different sheen and bought by the quart. A quart is a quarter of a gallon, about 85 to 100 sq ft at the label's rate.
When is primer needed?
On new drywall and patches, over stains, on bare wood, and for a big change in color. The drywall calculator works out the board for a new room.