A gel permeation chromatography (GPC) calculation method has been developed to determine the absolute molecular weight of a star-shaped styrenic block copolymer with GPC-ultraviolet/refractive index calibrated with linear polystyrene standards. To illustrate the simplicity of this method, we have synthesized nearly monodisperse, multiple-arm model polymers either by linking living polymeric arms with multifunctional silicon halide or by oligomerizing the p-chloromethylstyrene-terminated polystyrene macromonomers. The good agreement between the absolute molecular weight determined with this calculation method and that actually measured with a multi-angle laser light scattering device has corroborated the validity of the calculation method. (C) 2003 Wiley Periodicals, Inc.