For a 12×12 room with 8 ft walls, one standard door, two average windows and two coats, a two-gallon purchase is often a reasonable starting point when coverage is around 350 sq ft per gallon. Your exact result depends on openings, paint coverage, wall texture and whether the color change needs extra coats.
How to work it out
- Start with the 48 ft room perimeter.
- Multiply by wall height.
- Subtract doors and windows.
- Multiply by coats and waste.
- Divide by paint coverage and round up to whole gallons.
Example
A 12×12 room with 8 ft walls has 384 sq ft of gross wall area. After typical openings, two coats and a small waste allowance, the project often crosses the amount one gallon can cover, which is why two gallons is a common practical purchase.
Dark-to-light or light-to-dark color changes, porous repairs and heavily textured walls can reduce effective coverage.
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