Apparatus, including a pump system controller, features a signal processor or processing module configured at least to: receive signaling containing information about pump differential pressure, flow rate and corresponding power data at motor maximum speed published by pump manufacturers, as well as instant motor power and speed, for a system of pumps arranged in a multiple pump configuration; and determine corresponding signaling containing information about instant pump differential pressure and flow rate for the system of pumps arranged in the multiple pump configuration using a combined affinity equation and numerical interpolation algorithm, based upon the signaling received.