The goal of this study is to evaluate the limitation of ASTM D 198 bending and ASTM D 3044 in determinationof elastic modulus and shear modulus. Different material properties and span to depth ratios were usedto analyze the effects of material property and testing conditions. The ratio of true elastic modulus to apparentelastic modulus evaluated from ASTM D 198 bending sharply decreased with increment of span to depth ratio. Shear modulus evaluated from ASTM D 198 bending decreased with increment of depth, whereas shear modulusevaluated from ASTM D 3044 was hardly influenced by increment of depth. Poisson’s ratio influencedshear modulus from ASTM D 198 bending but did not influence shear modulus from ASTM D 3044. Differentshearing factor was obtained for different depths of beams to correct shear modulus obtained from ASTM D198 bending equivalent to shear modulus from theory of elasticity. Equivalent shear modulus of materials couldbe obtained by applying different shearing factors associated with beam depth for ASTM D 198 bending andcorrection factor for ASTM D 3044.