- Measure the dimensions of the surfaces to be painted and determine their square footage. A simple way to do this for a room with a uniform ceiling height is to measure the length of each wall, add the lengths together and multiply the sum by the height of the ceiling. For example, a square 10 foot by 10 foot room with a 10 foot high ceiling would be 40 feet times 10, or 400 square feet for the walls with another 100 square feet for the ceiling. The same concept works for exteriors, as well, but they may have to be broken into rectangles if roof heights are different on different parts of the house.
- Add all the square footages to be painted with the same color and paint type together.
- Subtract window and door openings from wall square footage as they will be painted with a different material or not at all. However, most pros do not subtract window and door openings, figuring the extra paint will account for loss in rinsing out brushes, pouring between containers and overall loss in roller covers. The extra paint will also be needed for touch ups.
- Obtain the coverage rate for the primer and paint of choice from the paint store or paint manufacturer's website.
- Divide the number of square feet to be painted by the coverage rate of the paint to determine the number of gallons needed.
- Multiply the number of gallons by the number of coats that will be needed for the job to determine the total amount of paint to purchase.
- Adapt the quantity of paint to be purchased to take advantage of possible savings by buying in different size containers. Custom tinted paint comes in quarts, gallons and five-gallon buckets. There is often a price break for buying in larger size containers. Aim not to have excess amounts of paint leftover.

## Things You Will Need

- Tape measure
- Calculator
- Paint coverage specifications