Days Of Supply Inventory, or DOS Inventory, is an important measure of a business’s ability to maintain healthy inventory levels. It’s calculated by dividing the number of units in stock—including both existing and backordered items—by the average daily demand for those same items. By looking at DOS Inventory, businesses can assess the speed with which their inventory is turning over, as well as identify any potential problems with overstocking or understocking of certain products. Having efficient DOS Inventory is an important part of running a successful business and staying on top of customer demand.