A calibration method for a bending machine having a bending angle measuring device, wherein a machine-based first coordinate system is associated with the bending machine, and the bending machine further having a bending tool arrangement, wherein during the execution of a bending process: • a light pattern is emitted from an illumination device of the bending angle measuring device onto a surface of a sheet metal part placed in the bending tool arrangement; • the image of the light pattern on the sheet surface is detected by an image capturing device of the bending angle measuring device; • and the detected image of the light pattern is analyzed by an evaluation module and a current actual bending angle is determined therefrom; • and if the current actual bending angle corresponds to a target bending angle determined according to a mathematical bending model, the bending process is stopped; characterized in that in a calibration process: • the light pattern is emitted by the illumination device onto a reference feature of the bending machine or the bending tool arrangement; • the image of the light pattern on the reference feature is detected by the image capturing device; • and a reference point of the reference feature is determined by the evaluation module from the captured image, which reference point is defined in the first coordinate system; • and a transformation matrix is determined by the evaluation module from the coordinates of the reference point in the first coordinate system and from a second coordinate system permanently associated with the bending angle measuring device; • and the transformation matrix is transmitted to a machine control of the bending machine and is taken into account by the machine control in the bending model of the bending process. • a light pattern is emitted from an illumination device of the bending angle measuring device onto a surface of a sheet metal part placed in the bending tool arrangement; • the image of the light pattern on the sheet surface is detected by an image capturing device of the bending angle measuring device; • and the detected image of the light pattern is analyzed by an evaluation module and a current actual bending angle is determined therefrom; • and if the current actual bending angle corresponds to a target bending angle determined according to a mathematical bending model, the bending process is stopped; • the light pattern is emitted by the illumination device onto a reference feature of the bending machine or the bending tool arrangement; • the image of the light pattern on the reference feature is detected by the image capturing device; • and a reference point of the reference feature is determined by the evaluation module from the captured image, which reference point is defined in the first coordinate system; • and a transformation matrix is determined by the evaluation module from the coordinates of the reference point in the first coordinate system and from a second coordinate system permanently associated with the bending angle measuring device; • and the transformation matrix is transmitted to a machine control of the bending machine and is taken into account by the machine control in the bending model of the bending process.