The interplay between crystallographic symmetry, structural distortions, and the tolerance factor derived from the isotropic ionic radii of the constituent cations and anions of inorganic perovskites and related materials is a ubiquitous concept in solid-state and materials chemistry. Here we demonstrate a model for the phase transition temperatures associated with these structural distortions in layered perovskites by considering the anisotropy associated with cations, which are susceptible to first-order Jahn-Teller distortions. These symmetry-lowering phase transitions are known to have a significant interplay with superconductivity in the high-