1. A system for estimating dynamic quantities, comprising: an electronic identification recognition apparatus for accessing a content of an electronic identification corresponding to a item placed into the system; a weight measuring apparatus for measuring a total weight of all items it carries; and a computing apparatus, coupled to the weight measuring apparatus and the electronic identification recognition apparatus, for receiving the total weight, such that a quantity of an individual item can be estimated and recorded by using the total weight obtained respectively before and after the individual item is stored and a recognition result obtained from the electronic identification recognition apparatus.