The theme of this graduate thesis is the „Calculation of the tank trailer”. The paper describes in short terms an overview of the tanks and their use in transport. Some of the individual components and use of the different materials were explained. Some of the basic shapes of the trailers and semi-trailers are shown. In order to get to know the subject of consideration as closely as possible, the basic elements for making a tank are presented. The analytical calculation was performed according to the standard EN13094:2015. In the paper dimensions of the vessel required for calculation was schematically presented. The analysis was performed for each part to make sure that the tank meets the conditions prescribed by the standard. For numerical calculation a model of entire tank was made. The three-dimensional model was made in the software package SolidWorks according to the documentation of the company Slisko. Before accessing the numerical calculation, all the necessary conditions for the calculation according to the standard. Numerical analysis is made for previously created geometry form SolidWorks and analysis for all loading conditions was made in the software package Ansys 18.1. In the analyzes, convergences were performed for solutions of the total equivalent von-Mises stress and total displacements for different finite element sizes. Optimization of supporting parts such as support of the king pin and supports on the chassis. After the optimization, the structure was re-analyzed according to the loading conditions on the optimized model. Through optimization the mass was reduce while the differences in stress and displacement are very small compared to the original structure.