ABSTRACT Young stellar clusters across nearly five orders of magnitude in mass appear to follow a power-law mass–radius relationship (MRR), $R_{\star }\propto M_{\star }^{\alpha }$, with α ≈ 0.2–0.33. We develop simple analytic model for the cluster relation. consider galaxy disc hydrostatic equilibrium, which hosts population molecular clouds that fragment into clumps undergoing formation and ...