How Much Paint for a 9x12 Room?
Paint needed
1.75 gallons
A 9 by 12 room with eight foot walls, one door, two windows, two coats.
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How that number is worked out
These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.
- Room perimeter, add all walls42 ft
- Wall height8 ft
- Doors1
- Windows2
- Coats2
- Coverage per gallon350 sq ft
Paint needed1.75 gallons
| Gross wall area | 336 sq ft |
|---|---|
| Less doors and windows | -51 sq ft |
| Net wall area | 285 sq ft |
| Area over 2 coats | 570 sq ft |
| Gallons, exact | 1.63 |
| Buy | 2 gallonsor 1 five gallon pail |
The material list this produces
| Paint, gallons | 2 |
|---|---|
| Primer, gallons (if bare or color change) | 1 |
| Painter's tape, rolls | 1 |
Coats compared
Coats is the input people get wrong, usually by hoping. Same room, one coat to three.
| Coats | Paint needed |
|---|---|
| 1 coat | 1 gallon |
| 2 coats | 1.75 gallons |
| 3 coats | 2.5 gallons |
What else matters here
Nine by twelve is the size a standard area rug is cut to, which is why so many bedrooms are built close to it. With one door and two windows the net wall area is 285 square feet and two coats comes to 1.63 gallons.
The two windows take 30 square feet out of the calculation and add an hour to the job. Every opening is a set of edges to cut in by brush, and on a room with two windows and a door the cutting in is comfortably longer than the rolling.
Deducting openings is worth doing on a room this size but not worth agonising over. A window taken as 15 square feet when it is really 12 changes the answer by less than a fiftieth of a gallon, which disappears in the rounding to the next quarter.
What this calculator assumes
- A door is taken as 21 sq ft and a window as 15 sq ft. Deducting them matters on a small room and barely moves a big one.
- 350 sq ft per gallon is the usual figure on a smooth primed wall. Bare drywall, textured walls and deep color changes all drink more, so drop it to 300 if any of those apply.
- Ceilings and trim are not included. Run the ceiling as its own area.
Questions people ask
How much paint for a 9x12 room?
About 1.63 gallons for two coats on eight foot walls with one door and two windows, so buy two gallons.
Should I deduct windows and doors?
Yes, it is easy and it is closer to right, but do not agonise over the exact sizes. Being a few square feet out per opening does not change what you buy.
How long does a 9x12 room take to paint?
A day for one person with two coats. Most of that is cutting in around the door, the two windows and the ceiling line, not rolling.
The paint calculator takes any dimensions you like and hands back the same list.