A comprehensive integrated simulator has been developed to simulate the riser and the regenerator of a fluid catalytic cracking (FCC) process. The gas-oil feed sent to the reactor of an FCC unit is cracked to yield gasoline and light fractions. The simulator predicts the yield of C-lump (C-1-C-4 + H-2), gasoline, light fuel oil, heavy fuel oil, regenerator temperature, coke burn-off, and the flue gas composition for different feed characteristics and operating conditions (temperature, pressure, catalyst circulation rate). It can also be used for trouble-shooting, optimization, and control of the process, so as to obtain the maximum yield of cracked products. The simulator integrates Weekman’s 10-lump kinetic model and plug flow hydrodynamics for the riser reactor with Errazu et. al’s grid model for the regenerator. A reactor-regenerator heat balance has been incorporated in the simulator to calculate the required catalyst to oil ratio. On testing the simulator over a wide range of operating conditions the predicted C-lump, gasoline, light fuel oil, and heavy fuel oil yields show similar results when compared with the existing Limited information in the literature.