The study of doping concentration in the carrier storage region of IGBT is considered desirable in many power converter applications. This Letter presents base doping profile estimation through investigation into transient base charge modeling of Non-punch through (NPT) Insulated Gate Bipolar Transistor (IGBT). Parabolic profile has been used for base carrier concentration which consequently leads to an analytical model for transient base charge decay of IGBT. The proposed model shows better consistency compared to the previously used linear model in all doping profiles. Finally, the implications of doping dependence on the base charge decay are explained, including implementation of doping profile estimation technique.