Bisphenol A polycarbonate was fractionated from methylene chloride solution by a progressive precipitation technique. The intrinsic viscosities of these fractions were obtained in methylene chloride solution and corresponded to a viscosity average molecular weight range of 2 × 103 to 80 × 103. The fractions were used to calibrate a gel permeation chromatograph, an experimental Q-factor of 23.8 was found. The calibration was further confirmed by membrane osmometry and light scattering experiments. The experimental viscosity data demonstrated that the Kurata-Stockmayer-Roig relationship is suited to interpret the molecular expansion of polycarbonate in methylene chloride.