Abstract: Mass of a payload delivered to a water-borne vessel is provided with high accuracy and without the need for human measurement or the need for personnel to enter the water. The draft of the vessel in an unloaded or empty condition is compared to a loaded or loading condition. A plurality of sensors positioned about the perimeter of the vessel's deck at a height above the waterline produce signals representative of their height above the waterline. These signals are then transmitted to a processor, which calculates the volume and mass of the payload utilizing volumetric equations and the payload's known density. In one embodiment, the sensors are coupled to radio transmitting devices that transmit the signals to the processor.