How to Estimate Paint Needs
- 1). Measure the length and height of the areas to be painted. Round off your figures to the nearest half foot and use a decimal figure -- for instance, 10.5 feet or 8 feet -- to make it easier to figure on the calculator. Remember, this is an estimate; you cannot measure your coverage to the inch, as there are too many variables like roller use and wall porosity.
- 2). Multiply the length and height of each wall, individually. This will yield the area to be painted. For a wall that's 9 feet by 12.5 feet, the area is 112.5 square feet.
- 3). Add together the areas of all the walls.
- 4). Add together the areas of the places you won't paint -- such as windows and entrances -- using the same method as Steps 1 through 3 to obtain the areas.
- 5). Subtract the area in Step 3 from that of Step 4. This is the estimated coverage you need. For example, if your area in Step 3 is 1,720 square feet, and your area from Step 4 is 335 square feet, your coverage area is 1,385.
- 6). Divide the coverage area by the coverage capacity of your paint. Use the 400 square foot figure for standard applications of normal household paint. Here, for 1,385 square feet, the result is about 3.5 gallons of paint, which would leave you half a gallon for later touch-ups or repairs.
Source...