Rule of Thumb Compressor Sizing for Horsepower Requirements

Rob Smith, System Specialist

We’ll start with the demand requirement and work our way back. What will the production equipment consume? This would be measured as CFM (Cubic Feet per Minute) and PSI (Pressure). As an example, if the machinery consumes 100 cfm @ 100 psi, the rule of thumb horsepower required for a screw technology compressor would be ~25, or about a 4:1 ratio of CFM/HP.

As a comparison for reciprocating piston technology compressors, the ratio is 3.5:1, CFM/ HP. So, for this application we would need a 30 HP compressor. These calculations are based on a 100 PSI system, if the pressure requirement is higher, then less air will be delivered…or more horsepower required.

Keep in mind that there are many variables that come into play when selecting an air compressor for a new application.

Some manufacturers are more efficient than others, hotter working environments produce less air, the length of piping and the number of bends add to the pressure requirement to overcome and deliver air to the production equipment requiring more horsepower, and many others.

At the end of the day it’s always wise to have a qualified System Specialist look over your requirements and assist in selecting the best equipment for your application.