Estimating casing wear for individual portions or lengths of a casing may take into account that individual drill string sections cause different amounts of casing wear based on the physical and material properties of each drill string section. In some instances, a method performed during a drilling operation may involve tracking a location of the plurality of drill string sections along the wellbore; corresponding a casing section with the drill string wear factors of the drill string sections radially proximate to the casing section the drilling intervals of the drilling operations; and calculating a drilling casing wear for the casing section based on the drill string wear factors corresponding to the casing section.