Abstract The preoperative assessment of anterior glenoid bone loss is a critical step in surgical planning for patients with recurrent anterior glenohumeral instability. The structural integrity of the glenoid has been identified as one of the most important factors influencing the success of operative repair. The currently accepted gold standard for glenoid structural assessment among most orthopaedic surgeons is the use of 3‐dimensional reconstructed computed tomography images with the humeral head digitally subtracted, yielding an en face sagittal oblique view of the glenoid. This view allows for evaluation of glenoid morphology and quantitative assessment of glenoid bone loss. In this article, we describe the practical application of ImageJ software (National Institutes of Health, Bethesda, MD) to quantify the amount of glenoid bone loss reported as a percentage of either total surface area or diameter. The following equations are used in this technical note for the diameter‐based method and surface area method, respectively: Percent bone loss = (Defect width/Diameter of inferior glenoid circle) × 100% and Percent bone loss = (Defect surface area/Surface area of inferior glenoid circle) × 100%.