Inventory

Improving Inventory Turns Without Starving the Line

Inventory turns measure how fast cash moves through your plant. Here is the math, the benchmarks, and the levers that raise turns without causing shortages.

Inventory turns is a cash number wearing an operations badge. Turns equal annual cost of goods sold divided by average inventory value: $24 million of COGS against $4 million of average inventory is 6 turns, and days on hand is 365 divided by 6, about 61 days. Carrying that inventory costs 18 to 30 percent of its value annually in capital, space, insurance, damage, and obsolescence, call it $1 million a year at the midpoint. Move from 6 turns to 8 and average inventory drops to $3 million, freeing $1 million of cash once and saving roughly $250,000 every year after.

Measure it honestly before improving it. Use COGS, not revenue, or margin inflates the answer. Use average inventory across at least 4 quarter-end points, or better, 12 monthly snapshots, because a single year-end reading is usually window-dressed 10 to 20 percent low. Then split turns three ways: raw material, WIP, and finished goods. A plant at 6 overall turns might run 12 on raw, 20 on WIP, and 3 on finished goods, and that split says the problem is the warehouse and the forecast, not the shop floor. The Inventory Turns calculator gives turns and days on hand from COGS and average inventory in one pass.

Benchmarks vary hard by industry, so compare within your lane. Job shops and heavy equipment run 3 to 5 turns. General discrete manufacturing runs 6 to 10. High-volume automotive suppliers run 12 to 20. Grocery and consumer packaged goods run 15 to 25. Percentile matters more than the absolute: moving from your industry's median to its top quartile typically means 30 to 50 percent less inventory at equal or better service. And always pair turns with a service metric; 10 turns with 88 percent on-time delivery is not an achievement, it is a shortage program.

The levers rank by leverage. Batch size first: cutting average batch size in half cuts cycle stock in half, and setup reduction is what makes that affordable. Lead time second: safety stock scales with the square root of replenishment lead time, so cutting a supplier from 8 weeks to 2 cuts the safety stock for that part by half. Then SKU rationalization: the bottom 20 percent of SKUs commonly hold 5 percent of sales and 25 percent of inventory. Then forecast and schedule discipline, because every schedule break creates a stranded pile somewhere.

The classic failure mode is cutting inventory by decree. An edict to take inventory down 20 percent by quarter-end gets you exactly that, followed by stockouts in week 3 of the next quarter, expedite fees, and a rebound to higher inventory than before. Inventory is an effect; batch sizes, lead times, forecast error, and minimum order quantities are the causes. The second failure mode is ignoring obsolete stock: dead inventory boosts the denominator forever, and most plants carry 5 to 15 percent of inventory value that has not moved in 12 months. Disposition it; it is already lost.

Also watch WIP, the turn killer nobody owns. WIP is set by Little's Law: WIP equals throughput times lead time, so a line shipping $80,000 a day with a 10 day internal lead time holds $800,000 of WIP by arithmetic, no matter what anyone wishes. Cut internal lead time to 4 days and WIP falls to $320,000. That is why lead time projects are inventory projects, and why plants that chase turns without touching flow time plateau within two quarters.

Run the cadence. Monthly: post turns and days on hand by category, review the top 20 part numbers by inventory value, and disposition anything unmoved for 6 months. Quarterly: reset safety stocks from actual lead times and forecast error, renegotiate the 5 worst minimum order quantities, and kill or merge the bottom decile of SKUs. Annually: benchmark against your industry quartiles and set the next year's target one quartile up. World-class means top-quartile turns for your industry with 97 percent plus on-time delivery, obsolete stock under 2 percent of value, and inventory decisions made from causes, not edicts.

Published 2026-07-02.