Short Glass Fibers (SGF) reinforced thermoplastic are increasingly replacing metals and its alloys with the advent of new polymer alloys and blends. Concurrently the product designs are also becoming more complex, increasing the dependence on simulation software. In order to obtain accurate mathematical and simulation results, experimental data have to be carefully integrated into mathematical models used in these software.The effect of varying weight percentage of SGF from 0 to 15% on tensile properties of the Acrylonitrile Butadiene Styrene (ABS) thermoplastic materials was evaluated using Moldflow simulation software and the results were compared with experimental and Finite Element Modelling Data. The Moldflow simulation software showed a drop in injection pressure above 10 wt.% SGF in ABS matrix. Experimental data also showed a drop in young's modulus above 10 wt.%.The Halpin-Tsai model for randomly oriented fibers showed an increase in young's modulus.Using the FEM approach, the reason for drop in injection pressure and young's modulus after 10 wt.% was analysed. It was observed that there is a critical inter-fibergap, below which the stress interaction effects begin to dominate and the stress between the fibers reaches the shear yield strength resulting in a drop in injection pressure and young's modulus. Critical inter-fiber gap for SGF-ABS composite is 60 micron.