399. Inventory Turnover
How many times the inventory “turns over” (is sold and replaced) per year. The single most-cited inventory metric.
Higher = leaner; lower = stagnant.
399.0.1. Definition variants
Three common formulations, depending on what data you have:
| Variant | Formula | Use when |
| Cost-based (most common) | Annual COGS / Avg inventory at cost | You have COGS data — most accurate |
| Sales-based | Annual sales / Avg inventory at sales price | You only have revenue, not COGS — less precise but works |
| Unit-based | Annual demand / Avg inventory units | Single-product analysis or ratio comparisons |
Cost-based is the standard for financial reporting; sales-based shows up in retail KPIs; unit-based is operational.
399.0.2. Why turnover matters
Turnover combines demand and inventory level into one number that captures capital efficiency:
- High turnover → inventory cycles quickly → low working capital tied up.
- Low turnover → inventory sits → cash trapped, risk of obsolescence.
Compare across products, sites, or time periods to spot trends.
399.0.3. Industry benchmarks
| Industry | Typical turnover | Why |
| Grocery / fresh food | 15-25 | Perishable, high-frequency replenishment |
| Apparel retail | 4-6 | Seasonal cycles, slow-moving items |
| Electronics retail | 6-8 | Moderate cycle, fast obsolescence |
| Industrial distribution | 4-8 | B2B, slower cycles |
| Heavy manufacturing | 3-5 | Long lead times, large WIP |
| Pharmaceuticals | 3-4 | Long shelf life, regulatory inventory |
| Luxury goods | 1-2 | Low volume, high margin per unit |
Use the benchmark to flag outliers. Far below benchmark → likely overstocked. Far above → may be understocked (frequent stockouts).
399.0.4. Connection to days of supply
The most natural “human-readable” interpretation of turnover is its inverse:
If turnover = 12, you hold 30 days of inventory. If turnover = 4, you hold 91 days. See [days_of_supply.typ](days_of_supply.typ).
399.0.5. What turnover doesn’t tell you
- Why the number is what it is — could be high turnover from good management OR understocking.
- Distribution across SKUs — total turnover hides which SKUs are dead stock vs fast movers (use FSN classification).
- Seasonality — annual averages mask quarterly swings (use seasonally adjusted turnover or rolling windows).
Turnover is a summary metric. Pair with stockout rate, FSN analysis, and days-of-supply distribution for diagnosis.
Example
Given:
- Annual COGS: $2,400,000
- Average inventory at cost (taken at month-ends, averaged): $200,000
Step 1 — turnover
Step 2 — interpret
Inventory turns over 12 times per year — once per month on average. Working capital tied up: $200K, cycling 12× → supports $2.4M in COGS.
Days of supply: days.
Step 3 — compare to benchmark
Industry: industrial distribution, benchmark 4-8.
This company at 12 is well above benchmark. Two interpretations:
- Lean operations: tight forecasts, fast replenishment, low safety stock. Excellent.
- Understocked: frequent stockouts, lost sales. Bad.
Diagnose with stockout rate and customer-feedback data. If stockout rate is < 2% → great efficiency. If > 10% → being lean is costing sales.
Step 4 — improve turnover (if it’s the goal)
Lever 1: shrink average inventory (numerator unchanged). Tighten safety stock, reduce cycle stock (smaller , more frequent orders), eliminate dead stock.
Lever 2: grow COGS without growing inventory proportionally — i.e., grow the business.
Lever 1 hits a floor (you need some safety stock). Lever 2 is where high-turnover companies actually win — Walmart, Costco, fast fashion all run high turnover by selling a lot from a small inventory footprint.