This bachelor's thesis focuses on the analysis of the effectiveness of cost calculation in a selected company, JASA Ltd., which is located in Benešov and specializes in international and domestic transport. The aim of the thesis is to identify shortcomings in the current calculation system and suggest specific measures to optimize it. This would lead to an increase of accuracy in calculation and effective cost management in the company. The theoretical part deals with the classification of costs, it analyzes the individual types and methods of calculations in detail and emphasizes their importance for effective financial management of the company. The company´s reports and guided interviews with the company's chief accountant represent the main data source. In the practical part of the thesis, an analysis of the current state of cost calculation in the company JASA Ltd. is performed. Consequently, some key issues are identified, such as an outdated operating overhead calculation model and failure to consider tire replacement costs in calculation leading to inaccuracies in the total cost calculation. Based on these findings, specific steps are proposed to optimize the calculation system, which include revising the model, updating input data on regular basis, and introducing other relevant cost items. Implementing these measures would lead to higher accuracy of calculations and more effective cost management, which would thus contribute to better management decision-making and support the long-term stability of the company.