The present invention relates to a method for calibrating a measuring microscope which may be used to measure masks, in which a calibration mask is utilized in a self-calibration algorithm in order to ascertain error correction data of the measuring microscope, wherein, in the self-calibration algorithm, the calibration mask is imaged and measured in various positions in the measuring microscope in order to ascertain one or more portions of the error correction data, wherein the surface profile of the calibration mask is ascertained and utilized when determining the error correction. Moreover, the invention relates to a measuring microscope and a method for operating same.