A high-precision ultrasonic flowmeter is proposed in this paper. The proposed techniques, including multi-phase time-zooming, improve the time accuracy of the water flow meter by up to x6. Additionally, the application of an active bandpass filter to the received ultrasonic wave reduces measurement variability by approximately x0.12. A prototype chip is designed and fabricated using 180 nm CMOS technology, achieving high measurement precision at a low cost and with low power consumption.