Paint: First determine the paintable surface area and subtract areas such as doors, windows and areas to be painted with another paint type or color. The rule of thumb is to subtract 20 square feet for each door and 15 square feet for each window. This will get it close enough. Figure 350 square feet per gallon. Additional coats of paint may be required if the walls are unpainted, heavily patched or dark in color. The calculator below is added for your convenience.
*Ceiling areas: Length x Width / 350 = # of gallons for one coat
*Wall Area: Add the length of each wall. Then multiply the total length by the height.
*Subtract each door (20 square feet each) and subtract each window (15 square feet each) from the area to find the actual wall area to be painted.
*Divide this figure by 350 square feet per gallon. If the remainder is less than .5, order a couple of quarts. If the remainder is more than .5 order an extra gallon.
*To paint woodwork: measure the length of trim in feet, multiply that number by .5 (1/2 foot) as rough size of width of trim. Round all numbers to nearest foot. Next determine the total length of moldings around the room. Multiply the sum by .5 and then divide this number by 350 to estimate the number of gallons needed.
*To paint doors: Use the same figure for estimating door coverage as is used in wall area calculations. (20 square feet = one door). Multiply the number of doors by 20, doubling the answer if you paint both sides. Wall paint estimates allow for 15 square feet for each window. Use 1/2 the window area to figure trim and inside sash. Glass does not figure into the calculations.
*For windows: Multiply the number of windows by 7.5. then divide by 350.
