A metering device meters and dispenses of a known volume of a liquid product. The metering device includes a receptacle and a moveable slug sized to fit within the receptacle, leaving a remaining volume within the receptacle equivalent to a desired amount of a liquid product to be dispensed. Application of a vacuum at the outlet end draws the known volume of liquid product out of the receptacle and causes the moveable slug to move from a first position at the inlet end of the receptacle to a second position at the outlet end of the receptacle. At the same time, additional liquid product is drawn in via the inlet aperture. When the vacuum is removed, the slug returns through the additionally drawn-in liquid product back to the first position.