Cutting tool wear constitutes one of the principal parameters in the processing cost of building stone. The life index of the cutting tool is obtained by evaluating the wear of diamond segments in the processing plants and examining the main parameters thereof. The purpose of this study is to determine the life index of the diamond cutting tool by considering the physico-mechanical properties of marble stones and the operational parameter of cutting speed. To this end, a dataset was provided by collecting the data from eight building stone processing plants in the provinces of Tehran, Isfahan, and Yazd of Iran. In this regard, the number of square metres of building stone that every diamond cutting tool can cut during its lifetime is defined as the cutting tool life index (TLI). After collecting the required data, SPSS software was employed for statistical analysis. The results revealed that the Brazilian tensile strength is the main parameter that affects the cutting tool life index. Linear and non-linear regression analyses were then considered for the development of predictive models for the TLI based on the Brazilian tensile strength. The performance of the developed models was subsequently examined by using three different criteria: the coefficient of determination, the variance accounted for, and the root-mean-square error. The results of this study show that the non-linear predictive model of the TLI presents a very good performance, and thus, the diamond cutting tool life index can be obtained for marble stones by considering the model developed herein.