This study investigated the sets of mental computation strategies used by prospective elementary teachers to compute sums and differences of whole numbers. In the context of an intervention designed to improve the number sense of prospective elementary teachers, participants were interviewed pre/post, and their mental computation strategies were analyzed. The analysis led to the identification of the "strategy ranges" used by the participants, as well as descriptions of changes pre/post in those strategy ranges. This article illustrates how strategy ranges, as an analytic tool, afford useful descriptions of the repertoires of mental computation strategies that individuals use.