If the supply lead time is certain and demand during the lead time is constant, a company would be able to set a reorder level such that it used the last item just as a new order arrived thus reducing holding costs to a minimum. The reorder level to do this is found as:

Reorder level is the level of inventory at which a new order for the item should be placed with the supplier

In an inventory control system, if there is uncertainty about the length of the supply lead time and demand during the lead time there might be following warning levels for inventory, to warn management that:

Supply lead time. This is the period of time between placing a new order with a supplier and receiving the delivery of the purchased items. The length of this supply lead time might be uncertain and might be several days, weeks or even months.

The EOQ can be calculated using a

Economic order theory assumes that the average inventory held is equal to one half of the reorder quantity

The EOQ is the quantity that minimises the sum of the annual order costs and the annual holding costs. The annual holding costs equal the annual order costs at this level

In the economic order quantity or EOQ model the equation D/Q calculates