An ultrasonic flow meter is disclosed, the ultrasonic flow meter including a flow tube with a flow channel for a fluid to be measured, and two ultrasound reflectors fixated inside the flow tube, a first ultrasound transducer, a second ultrasound transducer, and an electronic control arrangement for operating the ultrasonic flow meter. The ultrasound transducers and reflectors have relative positions and orientations forming an ultrasound path from the first ultrasound transducer to the at least two ultrasound reflectors, to the second ultrasound transducer, and vice versa. The ultrasonic flow meter measures absolute transit times of the ultrasound signal from the first ultrasound transducer to the second ultrasound transducer, and / or vice versa, and the ultrasound reflectors include at least 50% by weight of copper, and the ultrasound signal includes at least 8 pulses.