Home & DIY / Everyday tools
Plan your next fresh coat. Calculate paint for the four walls of a rectangular room, with openings and coats accounted for.
The working, clearly explained
Measure each room dimension in feet. Subtract the total area of doors and windows only once. Enter the coverage printed on your paint container; 350 sq ft per gallon is an editable starting assumption. The estimate excludes ceilings, trim, primer, spills and extra paint for touch-ups. Rough or porous surfaces may need more.
A 12 × 10 ft room with 8 ft walls has 352 sq ft of walls. Subtract 40 sq ft of openings, then apply two coats: 624 coat-sq-ft ÷ 350 = 1.783 gallons. Rounded up, that is two 1-gallon containers.
A 15 × 15 ft room with 9 ft walls, no openings and one coat at 400 sq ft per gallon needs 540 ÷ 400 = 1.35 gallons; buy two 1-gallon containers.
No. Calculate ceiling area separately as length × width, multiply by ceiling coats, then divide by ceiling-paint coverage.
Paint is sold in containers. The calculator rounds the estimate up to whole 1-gallon containers, not to the cheapest combination of available can sizes.