Paint Calculator
Gallons of paint needed for a room, minus doors and windows.
Check the can. 350 is typical; use 250 to 300 for bare or textured walls.
You need
1.7 gallons
Buy 2 gallon(s) to be safe, or round the remainder to quarts.
- Paintable wall area
- 301 sq ft
- Total area to cover (2 coats)
- 602 sq ft
Estimates only. Verify quantities before ordering.
How this is calculated
Wall area = 2 x (length + width) x ceiling height, minus 21 sq ft per door and 15 sq ft per window. Gallons = wall area x coats / coverage per gallon. The purchase figure rounds up to whole gallons.
This calculator estimates wall paint for a rectangular room. It computes the total wall area from the room dimensions and ceiling height, subtracts a standard allowance for each door (21 sq ft) and window (15 sq ft), multiplies by the number of coats, and divides by the coverage rate printed on the can.
Most interior latex paints cover 350 to 400 square feet per gallon on a smooth, previously painted surface. Drop the coverage number to 250 to 300 if you are painting bare drywall, heavily textured walls, or making a drastic color change, because the first coat will soak in more.
Paint for common room sizes
Rows assume 8 ft ceilings, one door, two windows, two coats, and 350 sq ft per gallon. Round up to whole gallons when you buy.
| Room size | Gallons | Wall area |
|---|---|---|
| 10 x 10 ft (small bedroom) | 1.5 gallons | 269 sq ft |
| 12 x 10 ft (bedroom) | 1.7 gallons | 301 sq ft |
| 12 x 12 ft | 1.9 gallons | 333 sq ft |
| 15 x 12 ft (living room) | 2.2 gallons | 381 sq ft |
| 20 x 15 ft (great room) | 2.9 gallons | 509 sq ft |
Common questions
How much does one gallon of paint cover?
About 350 to 400 square feet per coat on smooth, previously painted walls. Porous surfaces like new drywall, plaster patches, or heavy texture absorb more, so plan on 250 to 300 square feet per gallon for the first coat in those cases.
Do I really need two coats?
Almost always, yes. One coat rarely gives uniform color and sheen, even with paint-and-primer products. The exceptions are repainting with the exact same color or using very high-end paint over a similar shade. Budget two coats and treat one-coat results as a bonus.
Do I need primer as well?
Prime when painting bare drywall or wood, covering stains or repairs, switching from a dark color to a light one, or painting over glossy surfaces. If the walls are already painted, in good shape, and the color change is mild, a quality self-priming paint is usually enough.
Does this calculator include the ceiling?
No, it covers walls only, since ceilings are usually painted in a different product and finish. To estimate ceiling paint, multiply room length by width for the area, then divide by your coverage rate and multiply by coats. A 12 x 10 room ceiling is 120 sq ft, roughly a third of a gallon per coat.