A belt weighing system, including a belt passing over a weigh frame able to measure the weight of conveyed material, and at least one memory to store a zero image for the belt. At least one processor able to determine differences between a measured belt weight and a stored zero image for corresponding points or sections of the belt, and to determine if the differences are constant for different sections of the belt. A condition for an empty belt state can be detected where the instantaneous difference between the stored zero image and the measured belt weight for corresponding belt points or sections is equal to an average difference for different belt points or sections.