Inventory turnover

Inventory turnover measures how many times stock is fully renewed over a given period, usually a year. It is one of the most telling indicators of inventory health: high turnover means goods are not sitting idle, while low turnover signals tied-up capital, obsolescence risk, and wasted space. A single number tells you whether your stock is working for the business or against it.

How to calculate inventory turnover

The calculation is straightforward: you divide what went out over the period by the average inventory held during that period. In practice, you divide the cost of goods sold (or the volume shipped) by average inventory. A result of six, for example, means stock turned over six times in the year. From it you can easily derive coverage, the number of days of stock, by dividing the length of the period by turnover. Turnover and coverage are two sides of the same reality: one expressed in turns, the other in days.

How to interpret it

There is no universal “good” rate: turnover is always read against a sector and a product type. A grocery store turns over its stock far faster than a manufacturer of industrial parts. What matters is the comparison over time (is my turnover improving?) and across item families (which products are slow-moving?). Falling turnover signals overstock or weakening demand; very high turnover can, conversely, hide frequent stockouts. The metric raises the question; it doesn't answer it on its own.

When to track it in an SME

As soon as an SME ties up capital in stock, turnover deserves tracking, at least by broad item family. It is a typical management metric for the execution layer of the Two-Layer Model: it measures whether the inventory policy decided upstream actually has the intended effect on the ground, and shows where to act when it does not. Improving it family by family is a core part of inventory optimization.

The common mistake

The most frequent mistake is calculating a single overall turnover for the whole company and leaving it at that. That average hides the essential: a few fast-moving items can mask a large number of SKUs that sit idle. Turnover is only valuable when segmented, family by family. The other trap is reading it in isolation: high turnover is only good if service holds at the same time. A third error is chasing a target rate borrowed from another company or sector, without checking that it fits your own products, margins, and lead times. Out of context, such a figure means little.

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