A system for calculating and reporting slump in a delivery vehicle having a mixing drum 14 and hydraulic drive 16 for rotating the mixing drum, including a rotational sensor 20 configured to sense a rotational speed of the mixing drum, a hydraulic sensor 22 coupled to the hydraulic drive and configured to sense a hydraulic pressure required to turn the mixing drum, and a communications port 26 configured to communicate a slump calculation to a status system 28 commonly used in the concrete industry, wherein the sensing of the rotational speed of the mixing drum is used to qualify a calculation of current slump based on the hydraulic pressure required to turn the mixing drum.