DIO Calculator
Calculate Days Inventory Outstanding (DIO) — the average number of days a company holds inventory before selling it. DIO is a core working capital metric: lower is generally better because it means less cash tied up in stock.
What Is DIO?
Days Inventory Outstanding (DIO) — also called inventory days or days sales of inventory — measures how long, on average, a company holds inventory before selling it. It is the inventory component of the cash conversion cycle.
A DIO of 60 days means the company holds each unit of inventory for about 60 days before it sells. Lower DIO means faster inventory turnover, less cash tied up in stock, and lower storage and obsolescence costs. Higher DIO means slower sales and more working capital locked in inventory.
DIO Formula
DIO = (Average Inventory ÷ COGS) × Days in Period
Or using daily COGS:
DIO = Average Inventory ÷ (COGS ÷ Days in Period)
DIO is the inverse of inventory turnover: DIO = Days ÷ Inventory Turnover. Both describe the same relationship — one in days, the other in multiples per year.
Worked Example
A business has average inventory = $100,000, COGS = $600,000, and a 365-day period:
Daily COGS = $600,000 ÷ 365 = $1,643.84
DIO = $100,000 ÷ $1,643.84 = 60.83 days
Inventory turnover = $600,000 ÷ $100,000 = 6.00× per year
Cash tied up = $100,000 in average inventory
Interpretation: the company holds inventory for about 61 days before selling it. This is moderately efficient — below 60 days is often considered good, below 30 days is excellent for fast-moving goods. Reducing DIO to 30 days would free up roughly $50,000 in cash.
How to Interpret DIO
- Below 30 days (Excellent) — very fast turnover. Common in grocery, fresh food, and fast fashion.
- 30–60 days (Good) — healthy inventory turnover for most retail and distribution businesses.
- 60–90 days (Average) — acceptable, but there may be slow-moving SKUs or excess safety stock.
- 90–120 days (Slow) — inventory is sitting too long. Cash is tied up and obsolescence risk is rising.
- Above 120 days (Poor) — serious working capital problem. Consider discounting, writedowns, or a strategic review of product mix.
Frequently Asked Questions
What is a good DIO?
It varies by industry. Grocery: 15–30 days. Apparel: 60–90 days. Electronics: 45–90 days. Auto parts: 90–150 days. Furniture: 120–180 days. Compare against industry peers. Lower DIO is generally better, but too low can cause stockouts and lost sales — the optimal level balances cash efficiency with product availability.
What is the difference between DIO and inventory turnover?
They are inverses of each other. Inventory turnover tells you how many times inventory is sold and replaced per year (a multiple). DIO tells you how many days it takes to sell (a number of days). A turnover of 6× per year equals DIO of 60.83 days. Both describe the same underlying reality — use whichever is more intuitive for your analysis.
Should I use average inventory or ending inventory?
Use average inventory when you have both beginning and ending figures — it smooths seasonal swings and gives a more accurate picture. Ending inventory alone is a single point in time and can distort the calculation if the business has seasonal peaks (for example, retailers after Christmas). If only ending inventory is available, use it but note the limitation.
How can a company reduce DIO?
Several levers: stop stocking slow-moving SKUs, negotiate smaller and more frequent purchase orders with suppliers, use demand forecasting to align stock with sales, discount or liquidate excess stock, and tighten the product catalog. Many businesses improve DIO most by cutting the long tail of products, not by selling more of the top sellers.
Can DIO be zero or negative?
DIO can be zero if the business holds no inventory (service businesses, software companies). It cannot be negative — inventory cannot be less than zero. If a calculation gives a negative number, there is a data error (usually negative inventory or negative COGS from accounting adjustments).
How does DIO fit into the cash conversion cycle?
The cash conversion cycle (CCC) = DIO + DSO − DPO. DIO is the time inventory is held; DSO is the time to collect receivables; DPO is the time to pay suppliers. Together they measure how long cash is tied up in operations. Reducing DIO by 10 days shortens the CCC by 10 days, freeing up cash equal to 10 days of COGS.