How Much Paint Do I Need for a 12×12 Room?
October 24, 2026 · 6 min read
Gallons of paint for a 12×12 room with 8, 9 or 10 ft walls, one to three coats, with or without the ceiling, plus primer and when to buy quarts.
The quick answer
To paint the walls of a 12 × 12 ft room with 8 ft ceilings, one door and two windows, you need about 1.9 gallons for two coats, so buy 2 gallons. If you're painting the ceiling as well, add about 0.8 gallons, which in practice means one extra gallon of ceiling paint.
That assumes a typical coverage of 350 sq ft per gallon. Check the can, enter your own room size, number of doors and windows, and coats in our paint calculator, and it rounds up to the cans you actually need.
How to work it out
- Wall area. Perimeter × height: 48 ft × 8 ft = 384 sq ft.
- Subtract doors and windows. Allow about 21 sq ft for a standard door and 15 sq ft for a typical window: 384 − 21 − 30 = 333 sq ft.
- Multiply by the number of coats. Two coats: 333 × 2 = 666 sq ft of painting.
- Divide by the coverage on the can. 666 ÷ 350 = 1.9 gallons. Round up to whole cans: 2 gallons.
Don't subtract a closet door or a small window if you're not sure you'll skip it. Running out mid-wall means a second trip to the store, and a new batch that may not match exactly.
Coverage and coats change the answer
Paint labels give coverage as a range. Benjamin Moore, for example, lists its Regal Select interior paint at 400–450 sq ft per gallon with 1 or 2 coats. Rough, porous or patched walls soak up more, and so do big color changes. Here's how much the walls of the same 12 × 12 room need:
| Coats | Coverage per gallon | Paint needed | Gallons to buy |
|---|---|---|---|
| 1 coat | 350 sq ft | 0.95 gal | 1 |
| 2 coats | 400 sq ft | 1.66 gal | 2 |
| 2 coats | 350 sq ft | 1.90 gal | 2 |
| 2 coats | 250 sq ft | 2.66 gal | 3 |
| 3 coats | 350 sq ft | 2.85 gal | 3 |
Two coats is the normal plan for an even color and sheen. Budget for a third coat, or a tinted primer first, when you're covering a dark color with a light one.
Other room sizes and ceiling heights
Walls only, two coats at 350 sq ft per gallon, one door and two windows:
| Room | Wall height | Wall area | Paint needed | Gallons |
|---|---|---|---|---|
| 10 × 10 ft | 8 ft | 269 sq ft | 1.54 gal | 2 |
| 12 × 12 ft | 8 ft | 333 sq ft | 1.90 gal | 2 |
| 12 × 12 ft | 9 ft | 381 sq ft | 2.18 gal | 3 |
| 12 × 12 ft | 10 ft | 429 sq ft | 2.45 gal | 3 |
| 12 × 14 ft | 8 ft | 365 sq ft | 2.08 gal | 3 |
| 14 × 16 ft | 8 ft | 429 sq ft | 2.45 gal | 3 |
When you're only just over a whole gallon, like the 12 × 14 room at 2.08 gallons, buying 2 gallons plus a quart is usually cheaper than a third full gallon. Our room paint calculator rounds up to whole gallons, so use the exact figure it shows to decide.
Ceiling, primer and trim
- Ceiling. A 12 × 12 ceiling is 144 sq ft. Two coats at 350 sq ft per gallon is about 0.8 gallons, so one gallon of flat ceiling paint covers it.
- Primer for new drywall. Fresh drywall and joint compound need a coat of drywall primer before the color goes on, or the finish will look patchy. One coat over the walls of this room is about 1 gallon. If you're still at the drywall stage, see how many sheets of drywall a 12×12 room takes.
- Trim and doors. Baseboards, casings and a door take far less paint than the walls. A quart of semi-gloss or satin enamel is usually enough for one room.
Painting an older home? Check for lead
Homes built before 1978 may have lead-based paint under the newer layers. Sanding or scraping it releases toxic dust. Under the EPA's Lead Renovation, Repair and Painting (RRP) rule, anyone you pay to disturb painted surfaces in a pre-1978 home must be EPA lead-safe certified.
The rule generally doesn't apply to homeowners working on their own home, but the dust is just as harmful, so test first and use lead-safe work practices if the test is positive (EPA RRP frequent questions).
Painting tips that save paint
- Box your paint. Mix all the cans of one color together in a bucket before you start, so the color is identical on every wall.
- Cut in first, then roll. Brush a band along ceilings, corners and trim, then roll the walls while the edges are still wet to avoid visible lines.
- Keep a wet edge. Finish one wall at a time, working from wet paint into dry, rather than going back over areas that have started to dry.
- Save the leftovers. Label the can with the room and the date. A little matching paint makes touch-ups invisible later.
Planning the whole room makeover? Our square footage calculator gives you the floor area for new flooring, and our paint quantity calculator handles every other room in the house.
Sources & further reading
- Regal Select Interior Paint – Satin/Pearl (coverage and recommended coats) — Benjamin Moore
- Lead Renovation, Repair and Painting Program — US Environmental Protection Agency
- Frequent Questions on General Information About the RRP Rule — US Environmental Protection Agency