New correlations for the estimation of Henry's constants of nonpolar solutes in molten high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene TP), polybutadiene (PB), polyisobutylene PIB), polystyrene TS), poly(dimethylsiloxane) (PDMS), poly(vinyl chloride) (PVC), and poly(vinyl acetate) (PVAc), and those of polar solutes in LDPE, PS, PDMS, PVC, and PVAc were proposed. The new correlations only require the connectivity indices of the solutes in the calculation, which are more accurate and easier to apply than the existing correlations based on the physical properties of the solutes. Because connectivity indices can be calculated exactly once the chemical structure of the substance is known, the new correlations are more useful for molecular and process design and development.