Mass flow is the measure of the quantity of a material moving through an arbitrary system boundary (i.e. a control valve, tap, pipe, duct etc.) per unit of time. Mass flow rate is calculated by dividing the quantity of material flowing through the boundary by the duration of time taken to move through the boundary (i.e. ṁ = m/t).
Visit NASA.gov for a detailed description and visualisation of the mass flow concept.
Use our free online mass flow unit conversion calculator to easily convert between different units of mass flow including kilograms per hour (kg/hour), pounds per hour (lb/hour) and kilograms per second (kg/s) and tonnes per hour (t/hour).