The present invention is an apparatus for determining the flow rate of a fluid in a pipe. The apparatus includes a device for providing acoustic energy on a diagonal path through the fluid. The diagonal providing device is in contact with the pipe. The apparatus also includes a device for providing acoustic energy on a diametrical path through the fluid. The diametrical providing device is in contact with the pipe. The apparatus is also comprised of a device for determining the flow of fluid in the pipe based on the acoustic energy of the diagonal providing device and the acoustic energy of the diametrical providing device. In one embodiment, the diagonal providing device is fixedly disposed on the pipe. In another embodiment, the diametrical providing device provides acoustic energy emitted in both directions on the diametrical path. The diagonal providing device preferably includes a first transducer and a second transducer located at diametrically opposed positions about the pipe. The first transducer and second transducer are preferably adapted to alternatively function as transmitter and receiver so as to cause ultrasonic signals to travel through the fluid along the diametric path. The diametrical providing device preferably includes a third transducer and a fourth transducer located at diagonally opposed upstream and downstream positions relative to one another. The third transducer and the forth transducer are preferably adapted to alternatively function as a transmitter and receiver so as to cause ultrasonic signals to travel through the fluid alternatively in upstream and downstream directions along the diagonal path between the third transducer and the fourth transducer. The diametric path is adjacent to the diagonal path so that the transducers are sampling the same portion of fluid.