Loss of hydrostaticity limits high-pressure experiments, as pressure transmitting media (PTMs) solidify on compression. Here, we report a strong and positive correlation between the increase of molar density with pressure (ζ) at ambient conditions and the hydrostatic limit (HL) of isothermally compressed molecular liquids. This correlation is derived using molecular dynamics simulations and is validated against experimental values of ζ and HL. The positive (ζ)–HL correlation can be rationalized by writing ζ as a function of the molar density (ρ) and the pressure-induced decrease in molar volume (υ) as ζ= ρ2υ. While liquids are seen to not exhibit large ρand υ simultaneously, we find that large HL values originate mostly from large ρ, or, to some extent, from a large υ or from a trade-off between the two. At the molecular level, large ρand large υ are linked to low molecular sizes and to low characteristic frequencies of intermolecular vibrations (ω), respectively.