Painting a room
Pages in this list checked · How we check
Painting a room takes 5 of the pages on this site, not one. Wall area minus the openings, then coats, then cans. Subtracting the doors and windows is the step that decides whether you buy one gallon too many. Each page in the list computes its own figure from a published formula and prints the working, so the whole sequence can be checked rather than trusted.
- 1Paint CalculatorGallons for the coats you actually intend to doCalculator
- 2Square Footage CalculatorFloor and wall area for an irregular roomCalculator
- 3Drywall CalculatorIf the walls are not up yetCalculator
- 4How to Measure a Room for FlooringMeasuring around alcoves and baysGuide
- 5What Drywalling a Room CostsMaterials and labour, with the rangesGuide
What goes wrong on this job
Subtract the openings or buy a gallon too many
A 12 by 14 room with 9 ft ceilings has 468 sq ft of wall. One door and two windows remove roughly 55 sq ft, which is over a tenth — enough to change how many cans you carry home.
Coverage on the tin assumes a surface you probably do not have
The 350 to 400 sq ft per gallon printed on the can is for a smooth, previously painted, similar-coloured wall. New drywall drinks the first coat; a dark colour under a light one needs two regardless.
Ceilings are a different calculation
Floor area, not wall area, and usually flat paint rather than the wall finish, because a flat finish hides the joins a ceiling always has. A 12 by 14 ceiling is 168 sq ft — about half a gallon a coat, and it is the surface most often forgotten when the paint is bought.
A 12 × 14 room, 9 ft ceilings
| Surface | Area |
|---|---|
| Walls, gross | 468 sq ft |
| One door, two windows | ≈ 55 sq ft |
| Walls, net | ≈ 413 sq ft |
| Ceiling | 168 sq ft |
| Coverage per gallon | 350–400 sq ft |
Typical figures for orientation. Every one is recomputed by the calculators above from the dimensions you actually have.
What the figures rest on
Every quantity above is computed by one of the calculators in the list, from these published standards.