A method for determining calibration data for a grain-loss sensor on a combine harvester includes measuring grain-loss quantities, which were left behind by the combine harvester during a harvesting operation, and measuring sensor grain-loss values by the grain-loss sensor during the harvesting operation. Reference marks are assigned to the measured grain-loss quantities and the measured sensor grain-loss values and the calibration data for the grain-loss sensor are determined on the basis of a reconciliation of the measured grain-loss quantities with the measured sensor grain-loss values according to the reference marks.