A radiometric measuring device for determining a mass flow of a bulk material on a conveyor belt including, at least one detector which is configured to detect at least part of radiation of at least one radiation source the emits the radiation in a direction of the bulk material on the conveyor belt, the radiation having at least partially passed through the bulk material and the conveyor belt, at least one evaluation circuit which is configured to determine the mass flow of the bulk material based on the detected radiation; at least one storage means which is set up to store at least one measured value equation, the measured value equation mapping a relationship between the detected radiation and the mass flow, at least one electronic calculation means which is set up to determine, based on at least one calibration measurement without bulk material on the conveyor belt, a correction equation with which the measured value equation is corrected.