Performance of pneumatically driven vehicle depends on multiple factors, and efficiency of energy to work conversion in the pneumatic cylinder is one of them. This paper describes thermodynamic model of pneumatic cylinder. Equations that define cylinder's geometric properties, gas supply control parameters and energy conversion are presented. MATLAB scripts are included. LabVIEW user interface is presented, which allows altering of geometric and control parameters of the pneumatic cylinder in real time. The results of the simulation can be presented graphically and numerically.