A sonic- or ultrasonic flowmeter, suitable for replacement of differential pressure flowmeters, comprising: a pipe segment, to be connected to a first and a second pipe, each having a diameter, which complies to an industry standard for pipe diameters used in differential pressure flow measurement, having a length (L), which is equal to a standard length for a flow restricting element of a differential pressure flowmeter, having a diameter (D), which is equal to a standard for pipe diameters used in differential pressure flow measurement, comprising a first standard connector located on a first end of the pipe segment, and a second standard connector located on a second end of the pipe segment, a primary flow sensor, comprising at least one sonic- or ultrasonic transducer for transmission and/or reception of sonic- or ultrasonic signals through the pipe segment, mounted on the pipe segment, and a sensor electronic for providing a measurement signal representing a flow of fluid through the pipe segment, based on signals received by the sonic- or ultrasonic transducers.