Inventory Turnover Calculator
Compare COGS with average inventory value, calculate days inventory outstanding, and find slow-moving stock across items. Free and browser-only.
Turnover and stock holding
Use the same currency and cost basis for COGS and inventory. Period days apply to every result; carrying cost remains annual. Nothing is uploaded.
Turnover result
| Average inventory value(10,000 + 20,000) / 2 = 15,000 | 15,000 | (10,000 + 20,000) / 2 = 15,000 |
|---|---|---|
| Turnover in selected period90,000 / 15,000 | 6× | 90,000 / 15,000 |
| Days in COGS periodThe period covered by the entered COGS | 365 | The period covered by the entered COGS |
| Days inventory outstanding365 / turnover | 60.8333 days | 365 / turnover |
| Annual carrying cost15,000 × 25% | 3,750 | 15,000 × 25% |
| Review flagSlow if DIO > 90 days; positive stock with zero COGS is also flagged | Within threshold | Slow if DIO > 90 days; positive stock with zero COGS is also flagged |
Formulas and worked example
Average inventory value = (opening + closing) ÷ 2, or the arithmetic mean of supplied period values. Turnover = COGS ÷ average inventory value. Days inventory outstanding (DIO) = days in the COGS period ÷ turnover. Optional annual carrying cost = average inventory value × annual carrying rate ÷ 100.
With 90,000 COGS over 365 days, opening inventory 10,000 and closing inventory 20,000, the average is 15,000. Turnover = 90,000 ÷ 15,000 = 6×. DIO = 365 ÷ 6 = 60.8333 days. At a 25% annual carrying rate, carrying cost is 3,750 per year. It is within a 90-day threshold. Equally spaced snapshots of 10,000, 15,000 and 20,000 give the same average. Both examples are locked by tests.
Value turnover uses inventory at cost and COGS; unit turnover uses physical quantities. Different item costs or changing costs can make their ratios differ. Avoid mixing selling-price revenue with inventory at cost. A shorter measurement period changes DIO, so compare items using the declared period and review seasonality before labelling them slow movers.
FAQ
Why can unit turnover and value turnover differ?
Unit turnover is units sold or consumed ÷ average units in stock. Value turnover is COGS ÷ average inventory at cost. Costs weight items differently, and unit costs can change within a period. They coincide for an item with a constant unit cost and consistent measurements. Use COGS, not sales revenue, and value inventory on a compatible cost basis.
Why does the period length matter?
Turnover belongs to the period covered by COGS. DIO = days in that same period ÷ turnover. A quarterly ratio is not an annual ratio. The days setting applies to every bulk row, appears above the results, and is included in the CSV export.
How should several inventory values be averaged?
This tool takes the arithmetic mean of supplied snapshots, with equal weight per value. Use consistently spaced snapshots from the same period as COGS. Irregularly spaced observations need a time-weighted average calculated separately and entered as average_inventory.
How are zero COGS and zero inventory handled?
Positive average inventory with zero COGS has zero turnover and no finite DIO; it is flagged for review and ranked before finite DIO values. Zero average inventory makes turnover and DIO undefined, is labelled No inventory, and ranks last. These rows are explained rather than divided by zero.
Is carrying cost annual even for a shorter COGS period?
Yes. Annual carrying cost = average inventory value × annual carrying rate %. It is an annual estimate, not an expense prorated to the selected COGS period. Leave the rate blank to omit it. The rate may include capital, storage, insurance and shrinkage.
Is my data uploaded?
No. Calculations and CSV parsing run in your browser, and the numbers and files you enter are never sent to a server, unless you choose to share a link, which carries the single-item inputs in its address. The page has no ads, sign-up or third-party trackers; the site host keeps standard anonymous visit counts.
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