Inventory turnover: what turns tell you and what they hide

Definition decides the answer

Turnover compares consumption over a period against the stock held to support it, but both terms admit several definitions. Cost of goods sold against average stock at cost is the conventional pairing; using revenue against stock at cost inflates the result by the margin and makes cross-company comparison meaningless. Average stock computed from two period-end snapshots can also mislead badly where the business is seasonal, since both snapshots may fall at the same point in the cycle.

Aggregate figures hide the problem they are meant to reveal

A stable overall number can conceal fast lines turning rapidly and a growing pile of dead stock turning barely at all. The decomposition that matters splits turns by class, by category and by age, because those views separate healthy working stock from capital that is not coming back. A distribution of stock by age tells a management team more in one chart than a company-level ratio does in a year.

Comparison across businesses is usually invalid

Achievable turns depend on the business model: supply distance and lead time, breadth of range, service promise, product shelf life, and whether stock is owned or held on consignment. A distributor holding a deep spares range for immediate availability will never match a business shipping a narrow line direct from a nearby plant, and should not try. Benchmarks are informative only against genuinely comparable operations, and against your own trend.

Use it to ask questions, not to set the target

When turns fall, the productive response is to identify which component moved: order sizes, buffer levels, pipeline stock, ageing lines, or a demand shortfall against which stock was already committed. Each has a different remedy and a different owner. Setting turns as an objective without specifying which component should move invites the reflex of stopping purchases, which improves the ratio for a quarter and produces a service failure in the next one.

Frequently asked questions

Is days of inventory a better measure than turns?

It is the same information expressed as a duration, and it communicates more intuitively because people can compare it to lead times and shelf life. Both are subject to the same definitional traps, so what matters is consistency and decomposition rather than the choice between them.

Why does turnover fall when service improves?

Because higher availability is bought with buffer stock, and buffer sits still by design. This is not a failure but a purchase, and it should be reported as such: the relevant question is whether the availability gained is worth the capital it consumed.

How does consignment stock affect the figure?

Stock owned by a supplier but sitting in your facility is typically outside your balance sheet, which flatters your turns without changing the physical position. Comparisons therefore need to state whether such arrangements are included, or the improvement may be entirely an accounting effect.