Preferential solvation has become a useful tool to help characterize and understand the properties of liquid mixtures. Here, we provide a new quantitative measure of preferential solvation in binary and ternary mixtures that uses Kirkwood-Buff integrals as input, but differs from traditional measures. The advantages of the new measure are highlighted and compared with established literature approaches. Molecular dynamics simulations are performed to further investigate the nature of binary mixtures, as described by the new and existing measures of preferential solvation. It is shown that the new measure of preferential solvation is rigorous, has a simple physical interpretation, can be easily related to the underlying thermodynamic properties of the mixture, and naturally leads to zero values for ideal mixtures.