Abstract: The flow rate monitor includes a test line containing a chamber wherein the test line is declinated at a predetermined angle so stratification of liquid and gas will occur in the chamber. A sample stream is removed from the liquid in the chamber and provided to a separator which separates the gas from the sample stream to provide a gas output and a liquid output. The gas output and the liquid output is returned to the test line. The water cut of the liquid output is determined while the pressure of the composite petroleum stream is sensed along with the temperature. The volumetric flow rate of the composite petroleum stream is monitored and the flow rate signal is provided. The density of the composite petroleum stream is also monitored. The flow rate of all three coponents of the composite petroleum stream is determined in accordance with the temperature signal, the pressure signal, the water cut signal, the flow rate signal and the density signal.