<p>The point load strength index (I_s(50)), uniaxial compressive strength (UCS), and Brazilian tensile strength (BTS) of eleven types of red sandstone from the Hefei region, China, were determined under both dry and saturated conditions. I_s(50) exhibited strong correlations with both UCS and BTS across all test conditions. Among the evaluated regression models, the zero-intercept linear function was identified as the optimal formulation, as it not only provides a significant correlation but also aligns well with the underlying physical mechanisms. Subsequently, practical conversion formulas between Is₍₅₀₎ and UCS/BTS were established for dry, saturated, and combined conditions, respectively. The failure modes of red sandstone are complex and varied with the test method. In point load tests, rock specimen failure modes were classified as long-side failure, short-side failure, triple junction failure, and L-shaped failure, with long-side and short-side failures being the most prevalent. In uniaxial compression tests, the specimens primarily failed through multiple fracturing, multiple extension, multiple shear, and simple shear. The failure mode in Brazilian tensile tests was predominantly characterized by a central fracture. The softening coefficients determined from point load, uniaxial compression, and Brazilian tensile tests all decreased with increasing specimen porosity. For a given red sandstone, the softening coefficients obtained from point load and uniaxial compression tests are comparable, whereas the values derived from Brazilian tensile tests is relatively lower. This indicates that water saturation has a more pronounced weakening effect on the BTS of red sandstone.</p>