A system and method for controlling the speed of a recirculation pump in an anode recirculation loop of a fuel cell system based on a predetermined ratio of fresh hydrogen to recirculated anode gas. The system uses a model to determine the volume flow of the recirculated gas through a fuel cell stack to determine the recirculation rate based on a measured temperature of the recirculated gas, a measured pressure drop across a recirculation pump, a pressure drop across the anode inlet and outlet of the stack, a percentage of hydrogen in the recirculated gas, and the density of the recirculated gas.