A method of determining a flow rate of a pump involves determining a volume capacity for a flow line carrying produced fluids from the pump, determining a starting pressure for the flow line and setting an arbitrary target pressure for the purpose of testing. The test is initiated by preventing flow in the flow line while continuing to operate the pump and monitoring pressure in the flow line to determine a time interval required to reach the target pressure. The method then involves performing calculations to determine flow rate using the volume capacity, the starting pressure, the change in pressure over the time interval required to reach the target pressure. The flow rate is equivalent to ΔV divided by a change in time ΔT. The method is preferably used as part of a manual or automated pump control strategy to keep the pump operating within flow rate ranges that provide optimum pump efficiency.