Days inventory outstanding
How long stock sits before it is sold, on average.
01 What it is
Why anyone looks at this number
How long stock sits before it is sold, on average.
Inventory is cash you have already spent and cannot use. It also hides quality problems, forecasting problems and obsolescence until someone counts it.
02 The formula
How it is worked out
Days inventory outstanding = (inventory_value ÷ cogs) × days_in_period grain : month × plant × product group unit : days source : Inventory subledger and product costing
Value the numerator at cost, not at selling price, or the days will look far worse than they are.
03 Worked example
The same number, with real inputs
| Inventory at cost | €5.26m |
| Annual COGS | €32.0m |
| Days | 365 |
| Calculation | (5.26 ÷ 32.0) × 365 |
| Result | 60 days |
Two months of stock. Cutting four days releases about €350k — and usually exposes which product families are sitting still.
04 What moves it
Four things that actually change this number
Forecast accuracy
Every forecast miss becomes either stock you did not need or a sale you missed.
Batch and order sizes
Long production runs are efficient for the factory and expensive for cash.
Supplier lead time
Long lead times force safety stock, which is cash held as insurance.
Range breadth
More variants means more of everything held for the same total demand.
05 Where the number lives
The system, the record and the fields
| System of record | Key record | Fields you need |
|---|---|---|
| Inventory subledger and product costing | Stock item by plant and storage location | quantity_on_hand, valuation, movement_date, obsolescence_provision |
Value the numerator at cost, not at selling price, or the days will look far worse than they are.
06 How it goes wrong
Three ways this metric misleads people
One number for the whole warehouse
Fast movers and dead stock average into a comfortable-looking figure.
Fix: Split by product family and by ageing band; dead stock deserves its own line.Ignoring obsolescence
Stock held at full value that will never sell overstates both inventory and profit.
Fix: Provision on an ageing rule and report DIO before and after the provision.Using revenue instead of COGS
Dividing by revenue understates the days by whatever the margin is.
Fix: Always divide by cost of goods sold.08 Questions
Frequently asked
Is lower DIO always better?
No. Cut it too far and you start missing sales and paying for expedited freight. The right level is the one that holds your service promise at the lowest stock, which is a service-level decision, not a finance one.
How is DIO different from inventory turns?
They are the same information expressed differently: turns = 365 ÷ DIO. Days are easier to discuss with operations; turns are easier to compare across businesses.
One definition, everywhere it is used
SCIKIQ stores this metric once and serves it to every dashboard, board pack and agent that asks.