How much paint do I need for a room?
Add up the length of the walls you're painting and multiply by the ceiling height. Take off about 20 sq ft for each standard door and 15 sq ft for each window. Multiply what's left by the number of coats and divide by the coverage on the can.
Example: a 12' x 12' bedroom with 8' ceilings has 384 sq ft of wall. Remove one door and one window and you have 349 sq ft. Two coats is 698 sq ft of painting. At 350 sq ft per gallon that's just under 2 gallons — so buy 2 gallons, or a little more if you want paint left for touch-ups.
How far does a gallon go?
Most interior wall paints list 350 to 400 sq ft per gallon for one coat on smooth, primed drywall. Texture adds surface area and soaks up more paint, and bare drywall absorbs the first coat. Use the lower number for those, or the figure printed on your can.
| Surface | Typical coverage per gallon |
|---|---|
| Smooth, previously painted | about 400 sq ft |
| Typical drywall | about 350 sq ft |
| Light texture (orange peel, knockdown) | about 300 sq ft |
| Heavy texture or bare drywall | about 250 sq ft |
One coat or two?
One coat can be enough when you repaint the same or a very similar color over walls in good shape. For a color change, plan two. Going from dark to light, or painting a deep, saturated color, often needs a tinted primer first or a third coat.
When to use primer
Prime new or patched drywall, bare wood, stains, and glossy surfaces. A primer coat also helps when you're making a big color change. Primer usually covers a little less than paint, so the calculator uses about 300 sq ft per gallon.
Quarts, gallons or a 5-gallon pail?
A quart costs well over a quarter of a gallon, and a 5-gallon pail usually costs less than five single gallons. The calculator picks the cheapest typical mix that covers what you need — for example, one gallon plus two quarts instead of two gallons when you need about 1.4 gallons. If you buy several cans of the same color, pour them together in a bucket before you start so every wall matches.
Ceiling and trim
The ceiling is simply the room's length times its width; flat ceiling paint usually goes on in one coat. Trim and doors take less paint than you'd think — roughly 100 sq ft per quart. The calculator measures baseboards along the painted walls (skipping doorways), door and window casings, and door slabs on both sides.
Doing floors too? See the flooring calculator and the tile calculator.