A method and apparatus for measuring the flow rate of a fluid based on the fluid weight. A container is provided between a fluid source and a fluid removal system. A valve is arranged between the fluid source and the container, to control the admitting of fluid into the container from the source, and removal of fluid from the container by the removal system. The valve is controlled by a weight-responsive mechanism, which detects a change in weight of the container due to the admitting and removal of fluid, and opens or closes the valve accordingly. A flow rate of the fluid may be determined in terms of a time period between the closing and subsequent opening of the valve.