What Is Days Inventory Outstanding?
Days Inventory Outstanding (DIO), also called Days Sales of Inventory (DSI), measures the average number of days a company holds its inventory before selling it. It is a key efficiency metric in working capital management and a component of the cash conversion cycle. A lower DIO generally means inventory sells quickly, freeing up cash, while a higher DIO can signal overstocking or slow-moving goods.
How to Use This Calculator
Enter your average inventory value (typically the average of beginning and ending inventory for the period), your cost of goods sold (COGS), and the number of days in the period. Use 365 for a full year, 90 for a quarter, or 30 for a month. The calculator returns DIO in days plus the inventory turnover ratio.
The Formula Explained
$$\text{DIO} = \frac{\text{Average Inventory}}{\text{COGS}} \times \text{Days}$$ The ratio of inventory to COGS tells you what fraction of a year's worth of goods you are holding; multiplying by the days in the period converts that fraction into a number of days. Inventory turnover is the inverse relationship: \(\text{COGS} \div \text{Average Inventory}\), showing how many times stock cycles per period.
Worked Example
Suppose average inventory is $50,000, COGS is $365,000, and the period is 365 days. $$\text{DIO} = \left( \frac{50{,}000}{365{,}000} \right) \times 365 = 50 \text{ days}$$ This means it takes the business about 50 days on average to sell through its inventory, and turnover is \(365{,}000 \div 50{,}000 = 7.3\) times per year.
FAQ
What is a good DIO? It varies widely by industry. Grocery and fast-fashion retailers aim for low DIO (days to weeks), while heavy machinery may run months. Compare against industry peers and your own trend.
Should I use average or ending inventory? Average inventory (\((\text{beginning} + \text{ending}) \div 2\)) smooths out seasonal swings and is generally preferred, but ending inventory is acceptable for a quick estimate.
How does DIO relate to the cash conversion cycle? \(\text{Cash Conversion Cycle} = \text{DIO} + \text{Days Sales Outstanding} - \text{Days Payable Outstanding}\). DIO is the inventory leg of that cycle.
