61 days DIO—is StrojImport overstocked?
Not necessarily for import lead times. Compare to policy by class; C-class MOQ inflation may explain the rise from 54 days without A-class problem.
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Days Inventory Outstanding
Days Inventory Outstanding: plain-English definition, formula, worked example, how to interpret the result, peer-based benchmark guidance, common mistakes, and management actions in the ZBI Business Control Library.
What is Days Inventory Outstanding?
Days inventory outstanding (DIO) tells you how long inventory sits before it leaves as cost of goods sold—average inventory divided by COGS, multiplied by days in the period. It is not inventory turnover stated as times per year unless you convert. At StrojImport d.o.o. in Zagreb, EUR 200,000 average inventory against EUR 1.2M annual COGS over 365 days is about 61 DIO. I track DIO when purchasing argues for container loads and finance argues for overdraft—the same decision expressed in days and euros.
Why Days Inventory Outstanding matters
Every day of DIO is cash parked in the warehouse. Moving from 61 to 70 days on EUR 1.2M COGS ties roughly EUR 20,000 more stock without more sales. Slow DIO shows up in CCC before stockouts appear if you cut too deep. Customers feel high DIO as 'in stock' until obsolescence forces a fire sale that trains them to wait for discounts. Suppliers feel it when you delay payment because cash is in slow-moving SKUs. DIO is the inventory leg of working capital owners must manage with ABC discipline, not gut feel.
Formula and variables
DIO = (Average Inventory / COGS) × Days in Period
Average inventory — (opening + closing) / 2 or monthly average; match COGS period.
COGS — cost of goods sold for the same period as days (annual COGS with 365 days).
Days in period — 365 for annual view; 90 for quarter if COGS is quarterly.
Excel: =IFERROR(B2/B3*B4,0) — B2 avg inventory, B3 COGS, B4 days.
Real business example
StrojImport d.o.o., a EUR 4.5M industrial machinery parts importer in Zagreb, uses FY24 annual view: average inventory EUR 200,000; COGS EUR 1,200,000; 365 days. DIO = (200,000 / 1,200,000) × 365 = 60.8 days, reported as approximately 61 days. Prior year DIO was 54 days—EUR 45,000 extra stock sits mainly in C-class bearings ordered for MOQ, not demand. The inventory manager targets 58 days by Q2 by cutting two slow SKUs and shifting A-class to monthly review while keeping fill rate on hydraulic pumps above 97%.
How to interpret the result
DIO translates inventory euros into time—compare consistently with COGS and day basis.
- Segment by ABC class; headline 61 days can hide 120 days on C-class and 35 on A-class.
- Pair with stockout rate—DIO cuts that raise stockouts on A-class are false wins.
- Seasonal importers should compare same month prior year, not off-season to peak.
- Link DIO moves to CCC and cash need in the monthly management pack.
Benchmark context
MRO and machinery parts importers often run 45–75 DIO depending on import lead time and service level—peer average without your lead-time profile misleads. Benchmark against your trailing twelve months and against the DIO assumed in your credit facility. Five days above plan for two quarters usually precedes obsolescence write-offs or discounting.
Red flags
- DIO up 10+ days year-on-year with flat revenue—overbuy or demand miss.
- DIO improved but stockouts on A-class rose—cut in wrong place.
- DIO flat while obsolete inventory percent rising—slow movers masked in average.
- Import lead time doubled but DIO target unchanged—policy drift.
- DIO used alone without CCC—payables may hide inventory cash trap.
Common mistakes
- Using end inventory instead of average when COGS is annual.
- Mixing 365-day DIO with quarterly COGS without aligning days.
- Cutting A-class safety stock to hit a DIO target and raising stockouts.
- Excluding consignment stock that behaves like owned inventory.
- Comparing DIO across sites with different supplier lead times without adjustment.
What should management do next?
- Report DIO by ABC class monthly with stockout rate on A-class.
- Tie buyer MOQ exceptions to DIO and carrying cost impact before approval.
- Review slow movers above 90 days supply monthly with sales and finance.
- Include DIO assumption in annual stock build and cash flow forecast.
- Recalculate DIO after supplier lead-time changes within two weeks.
Related calculators
Related analyzers
Related templates & software
Related KPI pages
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FAQ
How does DIO relate to inventory turnover?
Turnover = COGS / average inventory; DIO = 365 / turnover for annual view. Same data, different expression.
Should I use 360 or 365 days?
Pick one and keep it—365 is common for annual external reporting alignment.
Can DIO be too low?
Yes if stockouts and emergency freight rise. Set floor by A-class service level, not only ceiling for cash.
Who owns DIO targets?
Inventory or procurement owns execution; CFO owns cash impact; sales owns fill rate on A-class—joint monthly review.
Summary
DIO shows how long inventory sits relative to COGS. Measure by class, align days and COGS period, and balance cash release against fill rate on critical SKUs.
Reviewed by ZBI Business Control Library · Last updated 2026-06-15