In this paper a new method for estimation of weight average molecular weight of polymer from mere intrinsic viscosity and GPC chromatogram of the sample was proposed. The method can be applied to narrow as well as broad distribution sample of polymers for which the constants of Mark Houwink equation are unknown. The metnod was tested using seven samples which have very different molecular weight distribution. The results calculated by the method are in excellent agreement with those obtained using universal calibration method which requires known constants of Mark-Houwink equation.