Self-blast circuit breakers utilize the energy dissipated by arc itself to create the required conditions for arc quenching during the current zero. The arc during high current phase induces nozzle ablation which causes pressure rise inside the circuit breaker. During the interrupting process of circuit breaker, the pressure in thermal chamber is characterized as one of the physical parameters of performances. To develop circuit breaker simulator, various tests for measuring pressure have been carried out by testing circuit breaker which could vary volume of thermal chamber, nozzle, and stroke speed. The measured pressure values from pressure rise test are compared with the results obtained from computational fluid dynamics (CFD) to validate the simulator code.