The common question can be compared to asking for the size of your engine in your car. It all depends on how you plan to use it. Many buyers refer to the size of their tank in terms of gallons. We'll begin with the size, but this is only a small part. The compressor's tank stores compressed air. Therefore, the larger the tank, the more time you can work with it without having to stop and fill the tank. A compressor that has a tank of one or two gallons will need to stop for refilling much more often than one with a larger, ten-gallon-or greater tank. A smaller tank will work well for jobs that do not require continuous pressure over extended periods of time. A spray painter will need a bigger tank to ensure that the paint does not get interrupted. Experts recommend using a 60-gallon or larger tank for spray painting cars, as it requires long, continuous applications.