Once the modulus of elasticity (MOE) when calculating the bending properties of plywood is obtained, the result is one of the requirements necessary in order to characterize these panels. For this purpose the A.S.T.M. D-3043 Standard establishes the span between the supports and the geometric characteristics of the samples. This is valid only if the modulus of elasticity is independent of sample geometry. The results obtained in this study demonstrate that the modulus of elasticity changes with these parameters (span and width). This report proposes a mathematical model including the experimental data which allows the representation of the variation in MOE as a function of the ratio: span between the support/width of the samples.