A block management method for OPC model calibration includes calculating differences in several different optical functions between first patterns of a first mask and patterns of a second mask corresponding to the first patterns but differing therefrom by a predetermined bias, selecting one or more of the optical functions based on the calculated differences, clustering data of variations in the values of the calculated differences in the selected ones of the optical functions, selecting respective ones of the first patterns in consideration of how the data clusters, and designating the selected first patterns as test patterns.