Paint calculator
Wall lengths, height, coats. Doors and windows subtracted. Answer in gallons, rounded the way you actually buy paint.
Tip: total wall length is the room perimeter for a full room (a 12x12 room is 48 ft).
Frequently asked questions
How much does a gallon of paint cover?
About 350 square feet per coat on smooth, primed walls, the number printed on most cans. Rough, porous, or unprimed surfaces drink more; dark-to-light color changes need an extra coat rather than thicker paint.
How many coats should I plan for?
Two coats is the standard for a uniform finish, and it is this calculator's default. One coat only works when repainting a similar color with quality paint.
How are doors and windows handled?
A standard door is about 20 sq ft and a window about 15 sq ft; the calculator subtracts those from the wall area. Trim, ceilings, and baseboards are separate jobs with their own paint.
Should I round up?
Yes, and the result does: paint is sold in whole gallons and quarts, touch-ups need leftovers, and a second trip to the store costs more than an extra quart. A 10% waste margin is built in.