Stock Turnover: Formula, Benchmarks by Retail Category and a Calculator

Stock turnover (stock turn in the UK, inventory turnover in the US) is the number of times a retailer sells through its average stock in a year. It is cost of sales divided by average stock at cost, and its mirror image, days of stock, says how long the average stock would last at the current rate of sale.

The formula fits on one line. What goes wrong is the basis of the two figures, the benchmark the result is compared with, and the chain total that averages away what each store is doing. This guide takes those in turn, with a calculator, category figures from the US Census Bureau and the turns of three large European retailers worked out from their own accounts.

1. The formula

Stock turnover = cost of sales for the period ÷ average stock at cost over the same period. Average stock is (opening stock + closing stock) ÷ 2 for a simple year; in a seasonal business, average the month-end figures instead, because a year that opens and closes in the quiet season understates the stock carried through the peak.

Days of stock = 365 ÷ stock turnover, or average stock ÷ cost of sales per day. Six turns a year is about 61 days of stock. For a period shorter than a year, divide by the days in the period and scale up: a month's cost of sales over the month's average stock, times 365 ÷ 30.

2. The common mistake: sales over stock at cost

Stock is carried at cost. IAS 2 measures inventories at the lower of cost and net realisable value, and the retail method it allows arrives at cost by taking the gross margin off the selling value³. Statistical series follow the same convention: the Census Bureau values retail inventories at cost and reports sales net of returns at selling prices². Divide sales by stock at cost and the result is not a turn: it overstates the true figure by 1 ÷ (1 − gross margin), which at a 50% margin is a factor of two.

The three figures come from Ahold Delhaize's annual report for 2025⁴, Kingfisher's results for the year to January 2026⁵ and H&M's full-year report for 2025⁶. They also show the second trap. Reported cost of sales is defined by each company: Ahold Delhaize includes purchasing, storage, rent, depreciation, salaries and the transport that brings stock to the point of sale⁴, so its turn computed from the income statement is higher than a turn on the cost of the goods alone. Compare a company with itself over time, and compare companies only after checking what their cost of sales contains.

3. Benchmarks by retail category

The most detailed public benchmark by category is the US Census Bureau's monthly inventories-to-sales ratio: end-of-month stock at cost divided by the month's sales^{1, 2}. A ratio of 2 means the stores hold two months of sales.

Two adjustments turn these ratios into turns comparable with your own. First, the ratio divides stock at cost by sales at selling price, so turns at cost ≈ 12 × (1 − gross margin) ÷ ratio: a clothing chain at a 50% margin and the category's 2.02 is turning about three times a year. Second, the stock includes warehouses serving the stores¹, so compare it with your stock in stores and distribution centres together, not with the shelves alone.

The more useful benchmark is usually internal: the same category in your other stores, and the same store last year. A category is a mix of products with different turns, and a benchmark tells you where to look, not what the figure should be.

4. One chain figure, many stores

A chain's turnover is total cost of sales over total average stock, which weights each store by its stock. Two stores can hold the chain figure in place while one turns its stock every month and the other every quarter.

Store 7 is holding stock that is not selling: the starting point is a dead-stock check by store, and then moving what sells elsewhere. Store 2 may be efficient or may be running empty: a high turn is also what out-of-stocks look like in the accounts, because the stock that would have sold was never there. The same reading applies one level down, product by product, which is where the decisions are actually made. Like the average ticket, the chain total is an average of very different stores.

5. How to raise it without emptying the shelf

• Find the stock that does not sell and act by kind: move it, stop reordering it, or return or mark it down.
• Size the buffer by supplier and product rather than by one rule for all: the safety stock guide shows why one factor overstocks reliable suppliers and understocks erratic ones.
• Order on a reorder point that covers the days until delivery, instead of topping every line up to a fixed number of days.
• Order smaller and more often where the supplier allows it: average stock falls with the order size.
• Watch availability alongside the turn, so a rise that comes from empty shelves is caught as one.

Turnover also connects stock to profit. Gross margin return on inventory (GMROI) is gross margin ÷ average stock at cost, which equals turnover × gross margin ÷ (1 − gross margin): at the same margin, every extra turn earns the same stock investment more.