Determining the mechanical strength properties of rock and rock-like materials is Impor for the analysis and design of mining and civil engineering projects. Although conventional experimental methods are accurate, their destructive nature, time-consuming procedures, and requirement for standard specimens limit their application during the early stages of design. In contrast, the ultrasonic pulse velocity method, due to its ease of implementation and ability to be performed in situ, serves as a suitable option for preliminary estimation of strength properties. In this study, the effectiveness of the ultrasonic pulse velocity method in estimating the mechanical strengths of four types of rock-like materials with different grain sizes was investigated. For each specimen, ultrasonic pulse velocity, uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), three-point bending (TPBT), and four-point bending (FPBT) tests were conducted, and corresponding regression models were developed. The results showed that the Turgut exponential model for compressive strength achieved a mean error of 6.64%, and the linear regression model demonstrated an acceptable fit with a mean error of 9.46%. Higher accuracy was obtained in estimating the Brazilian tensile strength (mean error of 3.65%). The three-point bending test exhibited the greatest scatter (17.67%), while the four-point bending test performed better (8.21%). Overall, the findings indicate that the ultrasonic pulse velocity method is reliable for estimating uniaxial compressive strength, Brazilian tensile strength, and four-point bending strength. Simultaneous comparison of four grain sizes and four mechanical tests enables the development of practical empirical relationships when destructive testing is constrained.