Exemplary embodiments of the present disclosure are directed to a system for measuring the capacity of a container. The system includes a variable scale disposed near or within the interior wall of the container with elongated body formed by an adjustable shaft including a number of visual indicators. The visual indicators are representative of a capacity of the container, and sliding the adjustable shaft adjusts an amount of space between each of the visual indicators. The system also includes a measuring arm extending from one end of the adjustable shaft and configured to rotate around an axis of rotation from a locked position, in which adjustment of the adjustable shaft is prevented, to a movable position, in which adjustment of the adjustable shaft is permitted. The measuring arm can be used to expand or compress the adjustable shaft, along with the spaces between the visual indicators.