According to the European Guidelines for quality control in digital mammography, mammographic image quality is expressed in terms of threshold contrast visibility using clinical exposure settings. The threshold contrast is defined as the lowest contrast value for which the objects are visible. The Contrast-Detail MAMmography (CDMAM) phantom is commonly used for the contrast-detail analysis, i.e. the detection of small thickness and low contrast objects. An automated scoring software tool (called CDCOM) was recently developed to evaluate the CDMAM radiographs. However, the CDCOM program does not determine the threshold contrast and further analysis is required by the user. This work presents a MATLAB-based graphical user interface (GUI), called CDMAM_fit_3, that a) reads and converts the original CDCOM data to a probability matrix, b) applies a psychometric curve fit to the data, c) predicts the human readout, d) compares the predicted results with the acceptable and achievable limits (provided by the European Guidelines) and e) saves the output data in various formats (i.e. txt, csv, xls, xlsx and xlsm). An executable version of the CDMAM_fit_3 can be used by the user without any programming and data processing knowledge.