Paint Calculator
Estimate how many gallons of paint a project needs.
Enter the total wall area you're painting, subtract the area of doors and windows, choose your number of coats, and you'll get the gallons needed. A gallon covers about 350 square feet per coat by default — adjust if your paint's coverage differs.
How it works
Paint needed = (wall area − openings) × coats ÷ coverage. Most interior paints cover 350–400 sq ft per gallon per coat. Two coats is standard for full color and durability, especially over a different base color. Always round up to whole gallons when buying.
Frequently asked questions
How much paint do I need?
Take the wall area, subtract doors and windows, multiply by the number of coats, then divide by the coverage (about 350 sq ft per gallon). A 400 sq ft room with 40 sq ft of openings needs about 2 gallons for two coats.
How much does a gallon of paint cover?
Roughly 350–400 square feet per coat on a smooth, primed surface. Textured or porous walls cover less.
How many coats of paint should I use?
Two coats is standard for even color and durability. One coat may do for minor touch-ups or repainting a similar color.
How much paint do I need for one wall?
Divide the wall's area by the coverage (about 350 sq ft per gallon per coat). A 12-ft-wide wall with 8-ft ceilings is 96 sq ft — about half a gallon covers two coats.
Is this calculator free and private?
Yes. Every CubicCabin calculator runs entirely in your browser, so the numbers you enter are never uploaded or stored. There's no sign-up, no limits, and it keeps working even if you lose connection after the page loads.