The calculation of Young's moduli of short fiber reinforced composites based on the Elementary Volume Concept (EVC) assumes that they are defined by the properties of the elementary volume. The elementary volume contains a single fiber having equal spacing to all neighboring fibers. For good fiber matrix adhesion one obtains aspect ratio dependent Young's moduli parallel and perpendicular to the fiber axis without any fitting parameters. For highly oriented quasi unidirectional short fiber reinforced composites as manufactured by push pull processing, the calculated and measured Young's moduli agree quite well, However, distinct differences occur in the case of conventionally processed short fiber reinforced composites with low preferential fiber orientation.