In heavily populated areas, cell splitting used to increase the capacity of the cellular system. Cell splitting produces a cellular system with mixed cell sizes. Many previous studies assumed strength-based power control, which maintains received power at a desired level regardless of changes in the number of active users and in the amount of total other cells interference. However, with signal-to-interference ratio (SIR)-based power control systems, that maintain the received SIR at a desired level, the power level is a function of the above two variables. This study calculates the reverse link capacity of SIR-based power control system with mixed cell sizes.