According to the Boston-based Product Stewardship Institute (PSI), about 10 percent of all household latex and oil-based paint goes unused in the U.S.—about 85 million gallons annually. PaintCare adds ...

Once you have your total, divide by 400 to determine how many gallons of paint you need for one coat of paint. Let’s practice and figure how how much paint is needed for a 12x12 room: 12 + 12 ...