How it’s calculated
- Wall area = Σ 2 × (length + width) × height − doors × 21 − windows × 15
- Gallons = (wall area + ceiling area) × coats ÷ coverage
- Primer (one coat) = area ÷ coverage
Worked example
One 12 × 14 ft room, 8 ft walls, 1 door, 2 windows, 2 coats at 350 sq ft/gal.
Inputs
- Rooms
- 12 × 14 ft
- Wall height
- 8 ft
- Doors (total, all rooms)
- 1
- Windows (total)
- 2
- Coats
- 2
- Coverage per gallon
- 350 sq ft
- Paint the ceilings too
- No
- Add one coat of primer
- No
- Price per gallon
- 0 $
Results
- Paint needed
- 2.09 gal
- Buy
- 2 gallons + 1 quart
- Paintable wall area
- 365 sq ft
Assumptions and limits
- Doors are 21 sq ft and windows 15 sq ft each.
- Trim, closets and textured surfaces are not included.
- Primer uses the same coverage rate as the paint; check the primer label.
Verify the result against the applicable local code, adopted code edition, manufacturer instructions and project requirements. See our methodology.
Questions
How many gallons of paint for a 12×14 room?
With 8 ft walls, one door and two windows, the walls are about 365 sq ft. Two coats at 350 sq ft per gallon need about 2.1 gallons — buy 2 gallons and 1 quart.
Do I need primer?
Prime new drywall, bare wood, stains, glossy surfaces, and large color changes. Painting over sound paint of a similar color often needs no primer.