How Much Paint for a 12x12 Room?
The short answer: about 2 gallons for two coats.
A 12x12 room with 8-foot ceilings needs about 2 gallons of wall paint for two coats. That assumes one door and two windows, which is typical. Add the ceiling and you are at 3 gallons. Add primer and you need 2 more gallons of primer.
Estimates only. Textured walls, high ceilings, sprayers and major colour changes can all increase the amount you need. Always buy slightly more than the calculation suggests.
Paint needed for a 12x12 room
| Room / surface | Surface | Coats | Paint | Paint cost |
|---|---|---|---|---|
| Walls only, 1 door, 2 windows | 333 sq ft | 2 | 2 gal | $70 |
| Walls only, 1 coat | 333 sq ft | 1 | 1 gal | $35 |
| Walls only, 3 coats | 333 sq ft | 3 | 3 gal | $105 |
| Walls and ceiling, 2 coats | 477 sq ft | 2 | 3 gal | $105 |
| Walls only, no openings subtracted | 384 sq ft | 2 | 3 gal | $105 |
Based on 350 sq ft per gallon and the standard allowances of 21 sq ft per door and 15 sq ft per window.
Where the 2 gallons comes from
A 12x12 room has a perimeter of 48 feet. Multiply that by an 8-foot ceiling and you get 384 square feet of wall.
You do not paint the door or the windows. Subtracting one door (21 sq ft) and two windows (15 sq ft each) removes 51 square feet, leaving 333 square feet of actual painted surface.
Two coats means buying enough for 666 square feet. At the standard 350 square feet per gallon, that is 1.9 gallons — which rounds up to 2 gallons.
When a 12x12 room needs 3 gallons instead of 2
Two gallons is comfortable, but not always enough. You are likely to need a third gallon if:
- You are painting the ceiling too — that adds 144 square feet, pushing the requirement to 3 gallons.
- You are going from a dark colour to a light one and need three coats.
- The walls are bare drywall or heavily textured. Use the 250 sq ft coverage setting instead of 350.
- You have more than two windows, or a large sliding door instead of a standard one.
Buying 2 gallons and running out at 80 % completion is the worst outcome. Paint mixed at the till is matched by tint code, but a second batch can still differ slightly. Buying the third gallon up front is cheaper than a mismatched wall.
What it costs
At $35 per gallon, the paint for a 12x12 room comes to about $70. Primer adds roughly $49 if you need 2 gallons of it. Budget another $30 for a roller, sleeve, tray, angled brush, tape and a drop cloth.
Realistically, expect $100 to $150 to paint a 12x12 room yourself, depending on the quality of the paint. A professional would charge several hundred dollars for the same room.
Frequently asked questions
Is 1 gallon enough for a 12x12 room?
For one coat, yes — barely. One gallon covers 350 square feet and the room has 333 square feet of wall. But one coat rarely looks right. For the standard two coats you need 2 gallons.
How much paint for a 12x12 room with the ceiling?
3 gallons. The walls need 2 gallons and the 144 sq ft ceiling adds roughly one more, plus a separate gallon of ceiling paint if you want a flat white finish.
How long does it take to paint a 12x12 room?
A single person can typically cut in and roll a 12x12 room in four to six hours per coat, including drying time between coats. Two coats is usually a full weekend day.
Do I need primer for a 12x12 room?
Only if the walls are bare, patched, stained, or you are covering a strong colour. On a previously painted wall in good condition, two coats of quality paint are enough.