Compressors having at least two compressor stages, a compressor discharge a first recycle flow path wherein the first recycle flow path connects the first compressor stage inlet feed and the compressor discharge, a second recycle flow path wherein the second recycle flow path connects the second compressor stage inlet feed and the compressor discharge, measurement devices sufficient to quantify a volumetric flow rate of the first compressor stage inlet feed, and a controller arranged and configured to accept a set of inputs, wherein the set of inputs comprises information sufficient to determine the work imparted by the first compressor stage, wherein the set of inputs is sufficient to quantify a volumetric flow rate of the second compressor stage inlet feed are described herein. Compressors having differing numbers of stages and the control of those compressors are also described.