A predictive framework is proposed for estimating the dipolarity/polarizability (pi*) values of binary mixtures via the relative normalized maximum absorption wavelength (Delta lambda(N)(mix)) of an indicator (N,N-dimethyl-4-nitroaniline) in the pure liquids and the pure component gas-phase dipole moments (mu). New spectroscopic measurements of 13 nonpolar (1)-polar (2) liquid mixtures are reported and local composition was used to correlate variations of Delta lambda(N)(mix) values with mole fraction, x(2). The resulting multivariate linear relationship in x(2) and mu allowed data correlation and was applied to prediction of pi* of (i) ten additional nonpolar-polar mixtures at temperatures of (15 to 45) degrees C, (ii) nine polar-polar mixtures, (iii) six CO2-expanded solvent mixtures, and (iv) five molecular solvent-ionic liquid mixtures and was found to give an overall deviation of 8.9% in pi* The predictive framework was applied to the dipolarity/polarizability scales of Effenberger-Wiirthner and Cataln for 16 polar-polar liquid mixtures and was found to give a maximum deviation of 9.6%. The predictive framework is widely applicable to chemical systems and requires only pure component pi* and gas-phase dipole moment values to estimate the dipolarity/polarizability of solvent mixtures.