Room paint calculator
Estimate a practical starting quantity with transparent assumptions you can adjust.
What this result is for
Use the estimate to prepare for a supplier conversation, compare project assumptions, or sanity-check quantities mentioned in a contractor proposal. It is not a substitute for site measurements or professional design.
How much paint for a 12 × 12 ft room?
With 8 ft walls, gross wall area is 384 sq ft. Subtract one 20 sq ft door and two 15 sq ft windows to get 334 sq ft. Two coats at 350 sq ft per gallon need 1.91 gallons before extra allowance. Two one-gallon cans cover that stated example; different coverage or an allowance may require more.
Walls, ceilings and fences are different measurements
This tool estimates interior room walls. Calculate ceilings and trim separately. For a fence, measure the actual paintable area of each side, account for gaps and edges, and use exterior-product coverage; room dimensions are not fence measurements.
What changes coverage?
Texture, porous surfaces, repairs and colour changes can increase usage. Follow the actual paint label and budget for primer separately where required.