Though extensively studied, hardness, defined as the resist ance of a material to deformation, still remains a challengi ng issue for a formal theoretical description due to its inherent mechani c l complexity. The widely applied Teter’s empirical corre lation between hardness and shear modulus has been considered to be not alwa ys valid for a large variety of materials. Here, inspired by t he classical work on Pugh’s modulus ratio, we develop a theoret ical model which establishes a robust correlation between h ardness and elasticity for a wide class of materials, including bulk metallic glasses, with results in very good agreement with e xperiment. The simplified form of our model also provides an unambiguous theoretical evidence for Teter’s empirical correlation.