Abstract: The invention concerns a system for real-time measurement of the instantaneous flow rate of a fluid with steady or unsteady flow in a conduit, comprising a flow member (1) for the fluid provided with at least two wall pressure taps (A,B), means (2) to measure pressure difference coupled with the two pressure taps (A,B), and programmed computing means (3) for real-time computing of flow rate by solving a nonlinear, ordinary, differential equation relating instantaneous flow rate to pressure difference, the pressure difference in said formula being positive or negative in relation to the variation in flow velocity of the fluid in the conduit and/or to the direction of flow of the fluid, characterized in that the flow member (1) comprises a filter (4) positioned between the two pressure taps (A,B) to increase pressure drop.