Density-functional theory is used to study homogeneous bubble nucleation in the stretched Lennard-Jones liquid. We show that the ratio of density-functional to classical nucleation theory free energy barriers should scale with the quantity Δμ/Δμspin, the difference in chemical potential between the bulk superheated and the saturated liquid divided by the chemical potential difference between the liquid spinodal and the saturated liquid. The critical bubble changes from classical near coexistence (sharp interface, uniform density that decreases with penetration into the coexistence region) to nonclassical beyond Δμ/Δμspin ≈ 0.5 (diffuse interface, increasing density with increasing penetration into the metastable region). The density at the center of the bubble, the mean bubble density, the bubble size, the interfacial thickness, and the free energy cost of forming a critical bubble all scale with Δμ/Δμspin in temperature-independent fashion. This precise measure of the degree of metastability should emerge as a natural parameter in data correlation, as well as in the development of improved theories of nucleation. © 2001 American Institute of Physics.