Inventory KPIs: The 7 Metrics That Actually Matter

The inventory KPIs that matter most are inventory turnover, days of inventory on hand, stockout rate, sell-through rate, gross margin return on investment (GMROI), carrying cost as a percentage of inventory value, and inventory accuracy. Together they answer four questions: is stock moving fast enough, are you running out, is it earning its keep, and do your records match reality? No single number tells the whole story, so the goal is a small dashboard of complementary metrics you watch as a trend and, crucially, per SKU rather than only company-wide.

A blended, once-a-quarter figure hides more than it reveals: a healthy company-wide turnover can mask fast movers you keep stocking out of and dead stock rotting in the C tail. Below are the KPIs worth tracking, what each one tells you, and the formula for each.

The core inventory KPIs at a glance

KPI	Formula	What it tells you
Inventory turnover	COGS ÷ average inventory	How many times a year you sell through stock
Days of inventory on hand	365 ÷ turnover	How many days one cycle of stock lasts
Sell-through rate	Units sold ÷ units received × 100	What share of a delivery actually sold
Stockout rate	Out-of-stock SKUs ÷ total SKUs × 100	How often you fail to fill demand
GMROI	Gross margin ÷ average inventory cost	Gross profit earned per dollar of inventory
Carrying cost %	Annual holding cost ÷ average inventory value × 100	What it costs to hold your stock
Inventory accuracy	Counted units matching records ÷ total counted × 100	Whether your data can be trusted

Which inventory KPI matters most?

If you can only track one, track inventory turnover, because it captures both halves of the balancing act: turn too slowly and cash sits in dead stock, turn too fast and you stock out. But turnover alone is a trailing average, so pair it with stockout rate to catch the fast movers it hides. The inventory turnover ratio guide walks through the calculation and what a good number looks like by sector.

How do you calculate inventory turnover?

Divide the cost of goods sold for a period by the average inventory over that period: turnover = COGS ÷ average inventory. Average inventory is usually beginning plus ending inventory, divided by two. Use COGS, not revenue: revenue includes your margin and overstates the ratio. A turnover of 6 means you sold and replaced your stock six times in the year, which is the same as a days of inventory on hand of about 61 days.

What is a good GMROI?

Gross margin return on investment tells you how many gross-profit dollars each dollar of inventory earns, and a GMROI above 1.0 means the inventory is at least paying for itself. Most healthy retailers target somewhere between 2.0 and 4.0, though the right number varies widely by category and margin. GMROI is the KPI that stops you from admiring high turnover on a product you sell at a loss: it forces margin and stock efficiency into the same number, which is why merchandisers lean on it more than turnover alone.

Why track stockout and sell-through rates?

Turnover and days on hand look backward at stock you already sold; stockout rate and sell-through look at demand you may be missing. A rising stockout rate is lost revenue and lost customers, and it often coexists with a healthy average turnover because a few SKUs are starved while others sit. Sell-through, the share of a delivery that sells in a set window, tells you whether you bought the right quantity in the first place. Both point back to the same fix: better forecasts and reorder points, which is the job of demand forecasting software.

Why inventory accuracy underpins every other KPI

Every KPI above is only as trustworthy as the counts feeding it. If your recorded stock does not match the shelf, your turnover, your reorder points and your GMROI are all built on fiction. Inventory accuracy, the share of counted items that match the system, is the KPI that keeps the others honest, and the practical way to hold it high without shutting the warehouse is cycle counting: counting a slice of SKUs continuously rather than everything once a year.

How often should you review inventory KPIs?

Review the operational KPIs, stockout rate and reorder signals, weekly, and the financial ones, turnover, GMROI and carrying cost, monthly, with a per-SKU view underneath the company-wide number. These metrics also travel well beyond operations: turnover and carrying cost feed straight into the working-capital story an owner tells when raising money or valuing a business, where lean, fast-moving inventory reads as a healthier balance sheet. Watching KPIs monthly and acting on them weekly is what separates a dashboard that decorates a wall from one that changes what you buy.

Computing these metrics per SKU and catching the lines quietly drifting the wrong way is a continuous job, not a quarterly spreadsheet. Our live stock scan reads your rows and returns per-SKU verdicts on cover, turnover and slow movers, so the KPIs that need action are the ones you see first. For the systems that track all of this automatically, see our inventory control software guide.