Inventory Turnover: What It Is and What's a Healthy Number by Category

The formula

Inventory turnover = Cost of Goods Sold (COGS) ÷ Average Inventory Value (at cost), for the same period.

Average inventory value is usually calculated as (beginning inventory value + ending inventory value) ÷ 2 for the period, to smooth out a single snapshot that might catch you unusually high or low.

Worked example

Annual COGS: $240,000. Beginning-of-year inventory value: $45,000. End-of-year inventory value: $35,000.

Average inventory value = ($45,000 + $35,000) ÷ 2 = $40,000.

Inventory turnover = $240,000 ÷ $40,000 = 6.0 — meaning, on average, you sold through and replaced your entire inventory value 6 times over the year.

Converting turnover into "days of inventory"

Turnover is more intuitive to most sellers once converted into days: Days of inventory = 365 ÷ turnover.

365 ÷ 6.0 = ≈61 days — on average, a unit of inventory sits for about 61 days between arriving and being sold.

Why "healthy" turnover varies enormously by category

There's no single universal target — a healthy number depends heavily on the product category's margin structure, shelf life, and typical purchase frequency:

• Perishable or trend-sensitive goods (fashion apparel, seasonal decor, anything with a short useful shelf life) need high turnover — slow-moving inventory in these categories loses value fast, whether through literal spoilage or simply going out of season/style.
• Consumables and fast-moving low-margin goods (household staples, some grocery-adjacent categories) typically run high turnover as a function of the business model — thin per-unit margin is made up in volume, and slow turnover erodes an already-thin margin quickly.
• Durable, higher-ticket, or slower-consideration-cycle goods (furniture, some electronics, specialty/niche products) commonly run meaningfully lower turnover — a lower number here isn't automatically a red flag the way it would be for a perishable category, because the purchase cycle itself is naturally longer.

Rather than chasing a single external benchmark number, the more useful practice is establishing your own category-specific baseline from your own historical turnover, and watching for a meaningful deviation from it — a sudden drop signals slowing sell-through or overbuying; a sudden spike can signal you're running leaner than your safety stock model intends and heading toward a stockout.

Turnover that's too high is also a warning sign

It's tempting to treat "higher turnover = better" as an unconditional goal, but turnover that's climbing because you're consistently running too lean often shows up alongside rising stockout rates and cancelled orders — that's not efficient inventory management, it's under-stocking. Read turnover alongside your stockout frequency and reorder point discipline, not in isolation.

Turnover that's too low ties up cash and space

Low turnover relative to your own baseline usually means capital sitting in inventory that isn't converting to revenue, plus (on marketplaces with storage fees) an increasing storage cost the longer it sits. See Overstock and Aged Inventory for what to do once you've identified slow-moving stock this way.

Using turnover to prioritize where you spend attention

Turnover calculated at the SKU level (not just overall) is one of the fastest ways to triage a large catalog: your lowest-turnover SKUs are your best candidates for a markdown or clearance review, and your highest-turnover SKUs are your best candidates for a safety-stock and reorder-point double-check, since they're the ones most exposed to a stockout if demand ticks up further.