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Days Inventory Outstanding (DIO) Calculator
DIO measures how many days a company holds inventory before selling it — the faster stock clears, the less working capital gets stranded on the shelf. Enter average inventory and COGS to compute DIO in days, view the equivalent inventory turnover, and read a plain-English interpretation of inventory efficiency.
Enter values in dollars (e.g. 500000 or 500K or 0.5M). Pull inventory from the balance sheet and COGS from the income statement for the same period. For Average Inventory, average the beginning and ending balances; a single period-end figure works as an approximation. Match the period selector to the time frame of your figures.
Enter your figures to calculate DIO
Input average inventory from the balance sheet and COGS from the income statement for the same period. The calculator returns DIO in days, the equivalent inventory turnover, and a color-coded interpretation of how efficiently the company converts inventory to sales.
RELATED TOOLS
Inventory turnover calculator — the ratio flip side of DIO →Cash conversion cycle — DIO + DSO − DPO in one number →Days sales outstanding — how fast the company collects from customers →DIO directly lengthens or compresses the cash conversion cycle — see how that flows through to intrinsic value in the discounted cash flow guide.
What Is Days Inventory Outstanding?
Days Inventory Outstanding tells you how many days, on average, a company holds inventory between purchasing (or producing) it and selling it. It is one of the three components of the cash conversion cycle — the others being Days Sales Outstanding (DSO) and Days Payable Outstanding (DPO). The formula is simple:
| Term | What it means |
|---|---|
| Average Inventory | The average of beginning and ending inventory balances — a period-end figure works as an approximation |
| Cost of Goods Sold (COGS) | Direct costs tied to producing the goods sold — the denominator that ties inventory to how fast it moves |
| Days in Period | 365 for annual, 90 for quarterly, 30 for monthly |
| = DIO | (Average Inventory / COGS) × Days — average days inventory sits before selling |
A lower DIO means faster inventory turnover and a tighter cash conversion cycle. Rising DIO, especially when sales are flat, is a red flag — it can signal weakening demand, overstocking, or inventory heading toward obsolescence. DIO is also just the inverse of inventory turnover expressed in days: DIO = 365 / Inventory Turnover.
How to Use This Calculator
Enter average inventory
Average the beginning and ending inventory balances from the balance sheet. A single period-end figure works as an approximation when only one is available.
Enter COGS
Use Cost of Goods Sold from the income statement for the same period as your inventory figure. COGS — not revenue — is the correct denominator because it is measured at cost.
Select the period
Choose Annual (365 days), Quarterly (90 days), or Monthly (30 days) to match your COGS and inventory figures. Mixing periods produces a meaningless result.
Read the verdict
The calculator returns DIO in days, the equivalent inventory turnover, and a color-coded interpretation from Excellent to High.
Key Concepts
DIO and the cash conversion cycle
CCC = DIO + DSO − DPO. Every day you shave off DIO reduces the cash conversion cycle by one day — freeing up cash that would otherwise sit in unsold inventory. Retailers like Walmart run tight DIO to keep the cash cycle short and even negative.
DIO is the inverse of turnover
DIO = 365 / Inventory Turnover, where turnover = COGS / Average Inventory. A turnover of 8× equals 45.6 days DIO; a turnover of 12× equals about 30 days. DIO is often more intuitive because it maps directly to how long stock sits before it sells.
When rising DIO is a warning
Watch for DIO climbing while sales are flat or falling — that combination signals overstocking, softening demand, or inventory drifting toward obsolescence. For products with shelf lives or fashion risk, a rising DIO can foreshadow future write-downs.
Frequently Asked Questions
What is Days Inventory Outstanding (DIO)?
DIO measures how many days a company holds inventory before selling it. Formula: (Average Inventory / COGS) × Days in Period. Lower DIO means faster inventory turnover and a tighter cash conversion cycle.
How do you calculate DIO?
DIO = (Average Inventory / COGS) × Days in Period. Use 365 for annual, 90 for quarterly, 30 for monthly. Example: $500K average inventory and $4M annual COGS gives (500,000 / 4,000,000) × 365 = 45.6 days DIO.
What is a good DIO?
Below 30 days is Excellent. 30–45 days is Good. 45–60 days is Average. Above 60 days is High. The right benchmark depends heavily on the industry — perishable grocers turn inventory in days, while machinery makers may hold it for months.
How does DIO relate to inventory turnover?
They are inverse views of the same metric. Inventory Turnover = COGS / Average Inventory. DIO = 365 / Inventory Turnover. A turnover of 8× equals 45.6 days DIO. DIO is more intuitive for tracking holding time; turnover works better for year-over-year efficiency comparisons.
How does DIO affect the cash conversion cycle?
CCC = DIO + DSO − DPO. A lower DIO directly compresses the cash conversion cycle because less cash is tied up in unsold inventory. Reducing DIO frees up working capital equal to the inventory no longer held — improving operating cash flow without changing the income statement.
FINISHED THE NUMBERS?
A calculator gives you one ratio. The report gives you the full picture.
DIO in context — inventory trends, cash conversion efficiency, and whether stock is turning faster or piling up — on any public company.
See a sample report →