Average Inventory Level

Average inventory is used to estimate the amount of inventory that a business typically has on hand over a longer time period than just the last month.

Average inventory is a calculation comparing the value or number of a particular good or set of goods during two or more specified time periods. Average inventory is the mean value of an inventory throughout a certain time period, which may vary from the median value of the same data set. 

(Current Inventory + Previous Inventory) / 2

Mostly the intended term is Average inventory cost.