Paint for a 12 × 13 ft room
This is a primary bedroom in a smaller house. With 8 ft ceilings the four walls have 400 ft² of surface, and after deducting one door (21 ft²) and two windows (30 ft²) there are 349 ft² to paint. The ceiling is 156 ft².
How the number of coats changes it
| Coats | Wall gallons | Buy for walls | Ceiling gallons | Buy for ceiling |
|---|---|---|---|---|
| 1 coat | 1.00 | 1 gallon | 0.45 | 2 quarts |
| 2 coats | 1.99 | 2 gallons | 0.89 | 1 gallon |
| 3 coats | 2.99 | 3 gallons | 1.34 | 1 gallon + 2 quarts |
If your ceilings are taller
| Ceiling height | Wall area | Gallons (2 coats) | Buy |
|---|---|---|---|
| 8 ft ceilings | 400 ft² | 1.99 | 2 gallons |
| 9 ft ceilings | 450 ft² | 2.28 | 2 gallons + 2 quarts |
| 10 ft ceilings | 500 ft² | 2.57 | 2 gallons + 3 quarts |
If your walls are rough or your paint covers less
The label on your can gives its coverage. Rough or textured walls and dark colors cover less, so the amounts go up:
| Coverage | Gallons (2 coats) | Buy |
|---|---|---|
| 250 ft² per gallon | 2.79 | 3 gallons |
| 300 ft² per gallon | 2.33 | 2 gallons + 2 quarts |
| 350 ft² per gallon | 1.99 | 2 gallons |
| 400 ft² per gallon | 1.75 | 1 gallon + 3 quarts |
Trim, tape and prep
The room is 50 ft around. Taping both the ceiling line and the baseboard is 100 ft of painter's tape, which is 1 roll of 60 yard tape. A quart of trim paint usually covers the baseboards and window and door casings for a room this size, and a gallon of primer is worth having for stains and patches.
Paint one wall at a time from the ceiling down, "cut in" the edges with a brush before rolling, and keep a wet edge to avoid lap marks. Let the first coat dry fully before the second, as the can directs.
A 12 × 13 room: right on the edge of the next can
A 12 × 13 ft room has 349 sq ft of wall after one door and two windows, and a ceiling of 156 sq ft. Two coats need 1.99 gallons for the walls, which means 2 gallons, and 0.89 gallons for the ceiling.
With the ceiling included the room takes 2.89 gallons. The wall figure lands so close to a round number that the label coverage decides it: a paint that spreads a little less than the 350 sq ft per gallon used here pushes the order past that, as the coverage table above shows. Read the can before you buy rather than after you run short on the last wall.
Want to change anything else? The calculator above is the full Paint Calculator: edit any number and the results update instantly.
Tools & materials for this project
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Frequently asked questions
How many gallons of paint do I need for a 12x13 room?
With 8 ft ceilings, one door, two windows and two coats at 350 ft² per gallon, the walls need 1.99 gallons, so buy 2 gallons. If you also paint the ceiling, add 0.89 gallons (1 gallon).
How much paint for the walls and ceiling of a 12x13 room?
Walls and ceiling together need about 2.89 gallons for two coats. That is 3 gallons if you use the same paint on both, though ceilings are usually painted with a separate flat ceiling paint.
How much primer do I need for a 12x13 room?
One coat of primer over the same walls is about 1.00 gallons (1 gallon). Primer often covers a little less than paint on bare surfaces, so check the can.
Related sizes and guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.