Based on the hard-sphere theory and an extensive literature database new correlations are developed to estimate the binary diffusion coefficients of liquid and solid solutes in supercritical solvents. The correlations can predict the behavior of the binary diffusion coefficients in a range of the reduced solvent density larger than 0.21, with an average absolute error of 7.8% for 107 systems and 1167 data points. The input data required for the correlations are the solute molecular weight, temperature, and density and the solvent basic properties (molecular weight, critical volume, and critical pressure).