# Days in inventory

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Days in inventory

Days in inventory(DII) is an efficiency ratio that measures the average number of days the company holds its inventory before selling it.

The formula for DII is:

$DII = \dfrac{average~inventory}{COGS/Days}$

where the average inventory is the average of inventory levels at the beginning and end of an accounting period, and COGS/day is calculated by dividing the total cost of goods sold per year by 365 days.[1]