A control system for a gas turbine includes a controller. The controller includes a processor configured to receive a plurality of signals comprising a temperature signal, a pressure signal, a speed signal, a mass flow signal, or a combination thereof, from sensors disposed in the gas turbine system. The processor is further configured to apply the plurality of signals as input to a heating value model. The processor is also configured to execute the heating value model to derive a heating value for a fuel combusted by the gas turbine system. The processor is additionally configured to control operations of the gas turbine system based on the heating value for the fuel.