The National Committee for the Accreditation of Scientific and technical terms defines a flowmeter as an instrument that indicates the flow rate measured and/or the total amount of fluid at a selected time interval. It is simply an instrument used to measure the flow of fluids in a pipe or nullah.

Flowmeter is divided into differential pressure flowmeter, rotor flowmeter, throttle flowmeter, slit flowmeter, volume flowmeter, electromagnetic flowmeter, ultrasonic flowmeter. Classification by medium: liquid flowmeter and gas flowmeter.