Polymer-filler interaction for nanocomposites was quantified by introducing Interface Area Function (IAF). to account for the nanofiller characteristics comprising of the specific surface area, correlation length and the filler volume fraction. IAF supplants the immeasurable filler characteristic terms, rendering tractability to the equation derived by considering the restraining forces acting on a nanofiller-elliptical platelet-embedded in polymer matrix. However, neglecting such terms reduces the same to Kraus's equation. Recognition of the due importance of such filler characteristics, by introduction of IAF, resulted in better fitment of swelling data and also conformance with the trend predicted by Zisman's interpretation of surface energy. Experimental values of Young's modulus of natural rubber and styrene-butadiene rubber nanocomposites and those predicted by Guth-Gold and Halpin-Tsai equations for composites conform post-introduction of IAF, with mere 5-20% deviations. The accurate fitment of the resulting constitutive equations indicates suitable integration of the shape and aggregate effects. (C) 2008 Elsevier Ltd. All rights reserved.