DIO Calculator

Formula

DIO = average inventory ÷ annual cost of goods sold × 365 days.

Worked example

With Average inventory value: 80000 currency units, Annual cost of goods sold: 400000 currency units/year, days inventory outstanding is 73 days.

Inputs and calculation

Use inventory valued on a basis compatible with cost of goods sold. Divide average inventory by the full-year COGS and scale that fraction of a year to days. The displayed relationship is DIO = average inventory ÷ annual cost of goods sold × 365 days. Keep the fields' displayed units attached when reproducing this relationship by hand.

Worked numerical example

For example, enter average inventory value 80,000 currency units, annual cost of goods sold 400,000 currency units/year. Those inputs produce days inventory outstanding of 73 days.

Holding the other example values fixed, change average inventory value from 80,000 to 88,000 currency units. The main output becomes 80.3 days. This comparison isolates the effect of that one input.

How to read and use the result

The result approximates how many days of sales cost sit in inventory. Lower is not automatically better if it causes stockouts or weaker service. Compare inventory efficiency across periods or similar businesses.

Practical context

Average inventory of 80,000 against 400,000 annual COGS corresponds to about 73 inventory days. A retailer holding fast-moving products and a manufacturer holding seasonal components should not be compared without considering their operating models. A rising DIO can signal overstock or obsolete items, but it can also reflect deliberate preparation for a sales peak.

Assumptions and scope

Inventory and COGS represent a comparable twelve-month period and accounting basis. Seasonal businesses may need more granular averages than opening and closing inventory alone. Replace the example defaults with measured inputs for your situation and account separately for factors outside these fields.

Checks and common mistakes

Do not divide inventory at selling prices by COGS at cost. Slow-moving or obsolete stock can also distort a high-level days figure.

Common questions

What should I verify before using the DIO Calculator result?

Reconcile inventory valuation and COGS from the same accounting records, then look at category-level turnover to locate the cause. The 365-day multiplier is appropriate when COGS is annual. If your COGS number covers a ninety-day quarter, use the matching quarter length instead; entering quarterly COGS here would overstate the days measure by roughly four times.

Sources and references

• OpenStax: Working capital and cash conversion