This thesis describes the code developed for the calculation of engineering constants and stresses and deformations that occur in a loaded composite material. In the introductory part, the composite materials and the field of their application are described. Some of the frequently used composite materials that are used in industry are described in more detail and their key properties are listed respectively. In the furter part of the paper, the mathematical expressions of the classical lamination theory are presented which are basis of the calculations of stresses. Mathematical expressions for the stress and strain calculations are intially presented with regard to the external loads influence and then those are expanded with hygrothermal infuences. Through the mathematical expression presentation the differences between isotropic, anisotropic and othotropic materials are presented. After the presented mathematical expressions, the software package MATLAB that is used is briefly described and the working principle of the developed code is described in detail using a flowcharts, afterthat there are shown some of the most important blocks of the program code . Furthermore, the verification of the developed code using software packages used in industry is presented. In the final chapter, a comparison of identically loaded equally thick plates made of steel and selected composite material is presented, and conclusions based on the obtained results are drawn.