We unveil universal correlations between architectural parameters and nonlinear elastic properties of brush polymer networks. A comprehensive library of poly­(n-butyl acrylate), poly­(dimethylsiloxane), and polyisobutylene brush networks was synthesized with systematically varied side chain length (∼n sc), grafting density (∼n g –1), and backbone degree of polymerization between cross-links (n x). This allowed experimental verification of theoretical scaling relationships between mechanical properties (shear modulus and strain-stiffening), architectural parameters n sc, n g, n x, and microstructure from in situ small-angle X-ray scattering in both comb and bottlebrush conformational regimes. These results can be used as a foundation for the programmable design of mechanically diverse solvent-free elastic materials.