Air compressor ratings commonly come in two types. There are differences in the measurements we come across as CFM and Standard CFM. For example, CFM is a smaller measurement in SCFM. Because the CFM is taken under pressure of 90 PSI and the air volume is therefore shorter. SCFM values are more massive. On the other hand, while SCFM is a volumetric flow rate according to a standard, there is no CFM standard.