A new universal calibration for gel permeation chromatography is proposed in which the hydrodynamic volume of the macromolecular chains is expressed by the quantity [eta]M/Phi instead of the commonly used quantity [eta]M (where [eta] is the intrinsic viscosity, M is the molecular mass, and Phi is Flory's parameter). Introducing Phi into the hydrodynamic volume is necessary because its value changes from one polymer to another when the polymers present a certain draining effect. The proposed procedure also allows the determination of Phi of any wormlike polymer. (C) 2003 Wiley Periodicals, Inc.