Pharmaceutical tablets are formed using various powder ingredients such as filler, binder, disintegrant, and active pharmaceutical ingredients (APIs). Tablets are formed by mixing the above ingredients followed by compaction. In the present study, powders' formulations were tested for its mechanical properties using a medium pressure flexible boundary cubical triaxial tester (CTT). Two types of triaxial tests, namely, conventional triaxial compression (CTC) and hydrostatic triaxial compression (HTC), were conducted at pressures upto 10 MPa. The data obtained from the CTC and HTC tests were used for determining the various fundamental elastic, elastoplastic, and rate-dependent properties. Tablets were formed at different pressures and their quality such as diametral strength, axial penetration strength, indentation hardness, and friability were measured. Some of the key findings were: bulk modulus increased with pressure and binder; shear modulus increased with confining pressure; tablet hardness increased with binder content upto a point and thereafter decreased or remained constant. Predictive regression equations for tablet quality vs. powders' mechanical properties were developed. All the powders' properties related with tablet qualities. Spring-back index, compression index, and bulk modulus were found most suitable for predicting diametral strength, axial penetration strength, indentation hardness, and friability.