Days Inventory Outstanding

The average number of days a company holds its inventory before selling it.

Days Inventory Outstanding (DIO) is a working capital metric that measures the average number of days a company takes to turn its inventory into sales. It reflects how long cash is tied up in physical goods sitting in warehouses or on store shelves. The metric is typically calculated on an annual or quarterly basis and is a core component of the cash conversion cycle, which tracks the overall timeline of cash flows from purchasing raw materials to collecting cash from customers. To calculate DIO, an analyst divides the average inventory held during a period by the Cost of Goods Sold (COGS) over that same period, then multiplies the result by the number of days in the period (usually 365 days for an annual calculation). Average inventory is used instead of ending inventory to smooth out seasonal fluctuations, and it is typically calculated by averaging the beginning and ending inventory balances from the balance sheet. For investors, DIO is a critical indicator of operational efficiency and product demand. A low or declining DIO is generally positive, suggesting that the company's products are selling quickly, which reduces storage costs, frees up cash, and minimizes the risk of inventory write-downs due to obsolescence. Conversely, a high or rising DIO can signal slowing consumer demand, overproduction, or poor inventory management, which can lead to future margin-eroding discounts, write-offs, and cash flow strain.

Company A has a beginning inventory of $70 million and an ending inventory of $90 million, resulting in an average inventory of $80 million for the fiscal year. Its Cost of Goods Sold (COGS) for the year is $400 million. Its Days Inventory Outstanding is calculated as: ($80 million / $400 million) 365 = 73 days.