The Solid Propellant Gas Generator (SPGG) is widely used for special military and space applications, in view of its simplicity, light weight, size and high reliability. A mathematical model that describes the burning characteristics inside the SPGG has been established and validated through the implementation of appropriate software. These two methods enabled to predict the performance and to draw the time variation of chamber pressure. An experimental work is carried out in order to prove the functionality and check the validity of the developed techniques. The comparison between the computational results and the experimental measured parameters showed a deviation error less than 4%. The presented software is considered as a powerful tool for selecting the SPGG design parameters in the stages of preliminary design and for performing further sensitivity analyses.