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Days Inventory Outstanding (DIO) measures how long, on average, inventory sits before it's sold — a key working-capital and operational efficiency metric, especially for retail and manufacturing businesses.
How it works
Enter average inventory and cost of goods sold for the period, and the calculator applies DIO = (Average Inventory ÷ COGS) × 365.
- Enter average inventory ($).
- Enter cost of goods sold ($, for the period).
- Click Calculate to see your results.
Examples
A retail inventory cycle
A business with $50,000 of average inventory and $400,000 of annual cost of goods sold has a DIO of about 45.6 days — inventory sits for roughly a month and a half before being sold, on average.
Who should use it
- Working capital and inventory management analysis.
- Comparing inventory efficiency across periods or similar companies.
Industry applications
- Retail and manufacturing operations
- Corporate finance and financial analysis
Advantages
- Expresses inventory efficiency in an intuitive "days" unit rather than an abstract ratio.
- Directly comparable across periods for the same business.
Limitations
- Most meaningful compared against similar businesses in the same industry, since "normal" DIO varies enormously by industry.
Common mistakes to avoid
- Using a single snapshot inventory figure instead of a true period average, which can distort the result for seasonal businesses.
- Comparing DIO across very different industries — a grocery business and a heavy-machinery manufacturer naturally have very different normal DIO ranges.
Best practices
- Use a genuine average (beginning + ending inventory, divided by 2) rather than a single point-in-time figure.
- Track DIO over multiple periods to spot a genuine trend rather than reacting to one period's number.
Tips
- Pair this with the Days Sales Outstanding and Days Payable Outstanding calculators to see a full cash-conversion-cycle picture, not just the inventory piece alone.