The aim of this study is to evaluate the transverse strain of hyperelastic solids as a function of its longitudinal using a special constitutive equation for compressible hyperelastic materials. In addition, the nonlinear dependence of the Poisson ratio on longitudinal strain was derived. Experimental data from EPDM elastomers subjected to uniaxial tension were used in order to determine the material parameters, which are incorporated in the constitutive law.