Basic Usage Calculations

On the surface, the Standard Cubic Feet Per Minute of an air compressor may seem to be the most important decision, since this determines how much air pressure you can expect at any given time. For commercial and contractor purposes, the SCFM of the air compressor has to meet or exceed the rating of the tools you plan to use. The simple calculation for this is to multiply the highest SCFM rated tool you will use by 1.5. Since the compression of air compressors is measured by pounds per square inch, compare compressors by the SCFM rating when the tank is filled to 90 psi. Except for small air compressors, you can set the desired psi on the tank up to the maximum rating of the compressor, which is why your initial calculation is multiplied by half again the desired pressure.

However, using multiple tools simultaneously will also increase the amount of compression power required. To allow for multiple tools, you will need to increase the SCFM of the air compressor,  the rate at which the tank is able to refill based on the horsepower of the compressor motor, or both. What these two figures mean is simpler than it may seem: SCFM determines how often the motor has to power up, while the HP determines how long the motor has to run in order to fill the tank. Both of these factors will be affected by the first real consideration you have to make, the tank size.