New equations for static light scattering of dil. binary solns. allow molar mass detn. of macromols. from measurements of scattered intensity ratios between soln. and solvent (Ir). In contrast to the std. Carr-Zimm equations, they do not rely on the exptl. abs. value of the Rayleigh ratio of a ref. liq. The picture shows a typical plot for the surfactant BRIJ72 in CH2Cl2 (MSupplier=0.359 kg mol-1). New static light scattering (SLS) equations for dil. binary solns. are derived. Contrarily to the usual SLS equations [Carr-Zimm (CZ)], the new equations have no need for the exptl. abs. Rayleigh ratio of a ref. liq. and solely rely on the ratio of scattered intensities of solns. and solvent. The new equations, which are based on polarizability equations, take into account the usual refractive index increment .vdelta.n/.vdelta.ρ2 complemented by the solvent specific polarizability and a term proportional to the slope of the soln. d. ρ vs. the solute mass concn. ρ2 (d. increment). Then all the equations are applied to 21 (macro)mols. with a wide range of molar mass (0.2\textlessM\textless8000 kg mol-1). On the studied dataset with M\textless200 kg mol-1, the new equations clearly achieve a better agreement with supplier M values. For macromols. (M\textgreater500 kg mol-1), for which the scattered intensity is no longer independent of the scattering angle, the new equations give the same value of the radius of gyration as the CZ equation and consistent values of the second virial coeff. [on SciFinder(R)]