The present invention provides a system for approximating the contents of a dispensing container. The dispensing container comprises a vessel 10 having a formation 20 and/or an element in or on the vessel such that when the vessel is laid on its side on a surface, the centre of gravity of the liquid contents causes the vessel to roll to a particular angle associated with that level, and an indicator 38 indicates the angle. The system further comprises a separate gauge 50, which interfaces with the container and co-operates with the indicator of the dispensing container, which signifies the approximate liquid contents of the vessel using a scale 54 on the gauge. The gauge may be a physical reference card with coloured segments 54a indicating the volume remaining. Alternatively the gauge may be a display on visual display unit. The display may show a digital reference card to be read by eye, or an image of the angle can be taken and automatically or manually compared to a local or remote reference image database and a result displayed on the screen. Alternatively the screen may be used to assess the distance travelled by the rolling vessel, and used to calculate the volume.
