Supply chain glossary
Days of Inventory Outstanding (DIO)
Financial metric that converts the value of inventory into days of cost of goods sold.
22. september 2026
3 min
Days of inventory outstanding (DIO) is a financial metric that says how many days of cost of goods sold a company is holding in stock. It is calculated as average inventory divided by COGS for the period and multiplied by the number of days in that period, which turns the balance sheet value of inventory into a figure expressed in time.
DIO is the mirror image of inventory turnover: 365 divided by turnover gives the same figure. Finance teams use it as the inventory leg of the cash conversion cycle, next to days sales outstanding and days payable outstanding, where it shows how long cash stays locked in goods before a sale releases it. Because the input is an average of accounting balances, one DIO figure describes a whole legal entity and says nothing about which categories or items the days sit in.
- DIO = (average inventory ÷ COGS) × days in the period
- DIO = 365 ÷ inventory turnover
- Cash conversion cycle = DIO + DSO − DPO
Days of inventory outstanding in practice
A DIO comparison means something only when both halves of the fraction are stable. The ratio falls when COGS grows faster than stock, so a strong sales year improves it without anyone changing how orders are placed, and it moves with the date of the balance sheet: a closing balance taken right after a season has been sold off gives a low number, while the same balance dated before the season gives a high one. Reading two figures off two annual reports without checking either input is the quickest way to the wrong conclusion.
The second limit is structural. A company does not manage DIO, it manages the components the days are made of: cycle stock driven by order frequency, safety stock driven by demand variability and lead time, and dead stock together with overstock, whose clearing speed is close to zero and which an average quietly absorbs. Splitting the days across those components turns the metric into a list of decisions – order cycles, target availability, write‑off rules – which an entity‑level number never produces on its own.
Demand forecasting and inventory optimization projects work at that level. Veritico STOCK sets target availability per segment, category or item, derives safety stock from three inputs (monthly forecast error, daily forecast variability and lead time uncertainty) and reports excess inventory in monetary terms, so days that can be removed stay visible separately from days that pay for service level. Expected inventory reduction in these projects is 15–30%.
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