Understanding Inventory Days of Supply
How we calculate. Days of supply = average inventory ÷ daily COGS (COGS/365). The form uses the same arithmetic as the worked examples on this page. See our methodology and accuracy policy.
Real-world scenario: A typical Inventory Days of Supply case uses average inventory 800000 and annual cogs / usage 4800000. Enter the same figures below to reproduce the worked path.
What is Inventory Days of Supply?
The companion to inventory turns (roughly 365 ÷ turns). Useful for buffer targets and cash-tied-in-stock conversations.
- Same cost basis as turns
- Annual COGS (or annualize a shorter window)
- Result in days
The Formula
Worked Example
Common Use Cases
- Working capital: stock cover
- Category planning: overstock flags
- S&OP: turns vs service tradeoffs
Pro Tips
- Annualize partial-year COGS
- Segment slow movers
- Pair with inventory turnover
Limitations: Inventory Days of Supply results are educational logistics and supply-chain planning aids—not SLAs, carrier contracts, or inventory valuation advice. Confirm definitions with your WMS/TMS and finance policies.
FAQ
Relation to turns?
If turns = COGS ÷ average inventory, DOS ≈ 365 ÷ turns when using a 365-day year.
What if COGS is 0?
Days of supply is undefined—enter positive COGS/usage.
Authoritative References
For logistics and supply-chain KPI definitions, consult:
- CSCMP — supply chain management resources
- ASCM / APICS — operations and inventory body of knowledge
- ISO 28000 — security management for the supply chain (context)