Days Inventory Outstanding Calculator
Days inventory outstanding (DIO) tells you how long, on average, inventory sits in your warehouse or on your shelves before being sold. Businesses with high inventory levels relative to sales have cash tied up in stock that could otherwise be used to pay expenses, reduce debt, or invest in growth. Understanding your DIO and comparing it to your industry benchmark helps you identify whether you are overstocking, and whether changes to ordering practices or supplier lead times could free up working capital.
Days inventory outstanding formula
Inventory Turnover = COGS / Inventory
Days Inventory Outstanding = (Inventory / COGS) * 365
Example: Inventory $120,000, COGS $730,000. Turnover = $730,000 / $120,000 = 6.08 times. DIO = ($120,000 / $730,000) * 365 = 59.97 days.
Managing inventory days
- Compare DIO to your supplier lead times. If lead time is 14 days but DIO is 90 days, you may be overstocking.
- Use DIO alongside DSO and days payable outstanding to calculate your cash conversion cycle.
- A sudden rise in DIO may signal weakening demand, product line issues, or supply chain delays.
- Just-in-time inventory systems aim to minimise DIO and reduce holding costs.
Frequently asked questions
What is days inventory outstanding?
Days inventory outstanding (DIO), also known as days inventory held or inventory days, measures the average number of days a business holds inventory before selling it. A lower DIO means faster inventory turnover and less capital tied up in stock.
How is DIO calculated?
DIO = (Inventory / Cost of Goods Sold) * 365. Inventory is typically the ending balance or the average of beginning and ending inventory for the period. COGS is from the income statement for the same period.
What is a good DIO?
A lower DIO is generally better, indicating inventory moves quickly. Typical ranges vary significantly: grocery stores may have DIO of 10 to 20 days while manufacturers may have 60 to 90 days. Compare within your industry and track the trend over time.
What causes a high DIO?
High DIO can result from overordering, slow-moving products, seasonality, supply chain disruptions, or weakening demand. Excess inventory also increases the risk of obsolescence and raises storage costs.
How is DIO related to the cash conversion cycle?
The cash conversion cycle (CCC) is DIO + DSO - DPO (days payable outstanding). It measures how long cash is tied up in operations. Reducing DIO is one way to shorten the CCC and improve free cash flow.
Official sources
- FASB ASC 330: Inventory.
- SBA: Manage Your Business Finances.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.