Inventory Turnover

Inventory — the goods held for sale or the raw materials and work-in-process awaiting completion — is a working capital asset that ties up cash and carries carrying costs including warehousing, insurance, financing, and the risk of obsolescence. Inventory turnover measures the velocity at which the company converts that inventory investment into cost of goods sold, providing a window into operational efficiency, supply chain management quality, and the balance between production and demand.

The standard formula is: Inventory Turnover = Cost of Goods Sold / Average Inventory, where average inventory is the mean of the period-opening and period-closing balances. Some analysts use revenue in the numerator instead of COGS, but COGS is more appropriate because both the numerator and denominator are stated at cost, ensuring apples-to-apples comparison. Dividing 365 by the turnover ratio yields days inventory outstanding (DIO) — the average number of days inventory sits before being sold.

What constitutes a 'good' inventory turnover is highly industry-dependent. A grocery chain like Kroger turns over its perishable inventory extremely rapidly — the industry average might be 12 to 15 times per year or roughly 25 to 30 days on hand. An aircraft manufacturer like Boeing may turn over its inventory once a year or less (300+ days on hand), which is entirely rational given the complexity and build time of commercial aircraft. Luxury goods companies deliberately maintain lower turnover to preserve scarcity perception around their products.

Deteriorating inventory turnover relative to a company's own history or its peers is a significant warning flag. If a consumer electronics company's inventory days are expanding, it may indicate that end-market demand is weakening, that the company misjudged production volumes, or that product mix has shifted toward slower-selling items. Inventory build-ups in the semiconductor industry in 2022 — as pandemic-era demand tailwinds reversed — caused dramatic earnings estimate cuts across the supply chain, from chipmakers to equipment suppliers.

Inventory accounting method also affects comparability: companies using FIFO (first-in, first-out) inventory accounting report different inventory values than those using LIFO (last-in, first-out), particularly in inflationary environments. Under LIFO, the balance sheet inventory figure may be significantly understated relative to current replacement cost, which can make LIFO users appear to have higher turnover than they actually do in economic terms. Adjusting for the LIFO reserve disclosed in the notes allows more accurate cross-company comparisons.