This paper presents some of our results regarding calculus of the functionally graded plates (FGPs). Such plates are made of Functionally Graded Materials (FGMs), which represent a new material class belonging to the composite materials. Our paper presents some material laws in a comparative way. But the main purpose of this paper is to provide calculus concepts and calculus methodologies, based on the means available in scientific research of mechanical engineering field, for the calculation of plates made of FGMs. Thus, the authors use the concepts of multilayer plate and equivalent plate, using both analytical and numerical calculus. The numerical method used are the Finite Element Method (FEM).The calculation aims both to determine the displacements and the stresses of the plates under statical loads, as well as to determine the free vibration frequencies. The research methodology is based on combining analytical calculation, where and when possible, with numerical simulation. The validation of our results is done by comparison with the analytical solution and the comparative analysis of the methods.