Abstract: The present invention pertains to a pourer spout, a use of the pourer spout, a method for measuring liquid outflow from a container, and an inventory system for liquids. The invention aims at solving the problem to keep track of the volume of liquids that has been dispensed from one or several containers. Basically, this problem is solved by providing each container with a pourer spout that determines the volume of the poured fluid. This is achieved by measuring the inflow of air into the container. The invention can e.g. be used for registering the dispensed liquor in a restaurant or a bar.