AbstractThe inherent viscosity of PVC resin in compounds containing fillers and additives can be calculated accurately and conveniently from the weight average molecular weight or the peak molecular weight as measured by High Performance‐Size Exclusion Chromatography (HP‐SEC). Molecular weight/inherent viscosity relationships are shown for typical production PVC resins. The utility of HP‐SEC instrumentation for the determination of IV for samples of commercial interest is demonstrated. Mark‐Houwink coefficients from the literature were used to calculate a convenient conversion factor of 0.612, which can be used to convert the molecular weight measured relative to polystyrene by HP‐SEC to the actual molecular weigh