The present invention relates to an apparatus and method for weighing crop on board a self-propelled harvesting machine. Specifically, the plurality of load cell assemblies are placed in the axle assemblies of the machine and are in communication with an intelligent control so that the weight of the harvested product contained in the hopper of the machine can be accurately weighed. A method for weighing harvested product on board a self-propelled harvesting machine is also disclosed using the apparatus described herein.