Residential painting – how many gallons do you need?
Whether you’re hiring a painting contractor or doing it yourself, it’s helpful to know how much paint it’s going to take to complete your residential painting project. For this blog, I’m going to concentrate on interior painting. No matter what aspect of your home you are painting – walls, ceiling, trim, doors, or windows, you’ll need to estimate the amount of paint needed to do the job right. There are specific calculations you can use for each surface you want painted or stained.
To estimate the amount of paint you need in order to cover the walls of a room, add together the length of all the walls and then multiply the number by the height of the room, from floor to ceiling. The number you get is the room’s square footage. Don’t worry – it’s easier than it sounds: length x height of walls.
Interior painting calculations
The next step is to figure out how much of that square footage is actually going to be painted (paintable surface area). Because you use a different paint on the doors and windows, subtract those areas from the room total. For average sized doors and windows just subtract 20 square feet for each door and 15 square feet for each window in the room. Very large custom doors or windows will of course be larger and you may want to consult a professional painter for a more accurate assessment.
Finish painting considerations
Usually if you’re using quality paint you can expect 1 gallon to cover about 350 square feet. If the walls are unpainted drywall they will absorb much more paint so you may want to err on the side of caution. Of course, if you’re planning on using 2 coats, you’ll need to double your number. Unsure how many coats you will need? If you’re painting walls that are unfinished, heavily patched, or creating a drastic color change, 2 coats is probably your best bet.
House painting – rounding up the gallons
The last step is to divide the paintable wall area by 350 (because that’s roughly the square-foot coverage in a gallon can, remember?) to find the number of gallons of paint you need for the walls. You can round uneven numbers; if the remainder is less than .5, you may need a couple of quarts to go with the gallons; if the remainder is more than .5, it might be a better bed to plan on an extra gallon (especially if you have very large or custom made doors and windows). Homeowners may be surprised that buying in bulk can be much more economical, so you may discover that 3 quarts of paint cost as much as a gallon.
Professional painting help
If you’re like me and math is not your strong suit, I found a nifty calculator online here. This calculator is a great way to get a quick and easy round number so you can roughly calculate how much paint you’ll need if you have pretty standard sized and shaped rooms.
If you have a larger or more intricate project, calling for a free painting estimate from a licensed house painter might be your best option.