Retail metrics explained: sell-through, GMROI and weeks of cover
Three metrics answer most questions about how fashion stock is performing. How to calculate sell-through, GMROI and weeks of cover, and read them together.
KEY TAKEAWAYS Summary by the editors
- Sell-through measures the share of stock sold in a period and is the main signal for re-order and markdown decisions.
- GMROI divides gross margin by average inventory at cost, combining margin and stock turn into one measure of return on stock investment.
- Weeks of cover divides current stock by recent weekly sales and is the forward-looking metric for replenishment and allocation.
- Each metric can mislead on its own, so they should be read together, by size and net of returns.
- Brands and retailers should agree metric definitions before sharing performance data.
A buyer reports that a style has sold well. The planner asks how well: what share of the stock sold, at what margin, and how quickly? Those questions are answered by a small set of metrics that every fashion retailer, and every brand selling to retailers, should understand precisely. Sell-through, GMROI and weeks of cover are the most important of them, and they are most useful when read together.
What is sell-through and how is it calculated?
Sell-through measures the proportion of stock that has been sold over a period. The most common definition is:
Sell-through (%) = units sold ÷ units received × 100
For example (illustrative), if a store received 200 units of a style and sold 120 in the first six weeks, its sell-through for that period is 60%. Retailers define the base differently: some use units received, others opening stock plus receipts. What matters is applying one definition consistently.
Sell-through is usually tracked weekly, with full-price sales separated from markdown sales. A high full-price sell-through early in the season is a strong signal to re-order; a low one suggests the style may need repricing, better placement or a transfer to stores where it sells.
What is GMROI and why does it matter?
Gross margin return on inventory investment (GMROI) shows how much gross margin a retailer earns for each unit of currency invested in stock, valued at cost.
GMROI = gross margin ÷ average inventory at cost
For example (illustrative), a category that generates 300,000 of gross margin over a year while holding an average inventory of 150,000 at cost has a GMROI of 2.0: every 1 invested in stock returned 2 in gross margin.
GMROI combines margin and stock turn into a single figure. A category with modest margins can achieve a strong GMROI if it turns quickly, while a high-margin category that sits on the shelf may deliver a poor return. That makes it particularly useful for comparing brands, categories or suppliers that differ in both price positioning and rate of sale.
What are weeks of cover?
Weeks of cover, also called weeks of supply, shows how long current stock would last at the current rate of sale.
Weeks of cover = current stock ÷ average weekly sales
For example (illustrative), a style with 400 units in stock selling 50 units a week has 8 weeks of cover. If only 4 weeks of full-price selling remain, the retailer holds too much and should consider transfers or promotion. If 12 weeks remain and the style is a proven seller, a re-order may be needed.
Weeks of cover is forward-looking, which makes it the operational metric for replenishment and allocation. It should be calculated on recent sales, typically the last few weeks, since a rate averaged over the whole season can hide acceleration or decline.
| Metric | Formula | What it tells you | Typical use |
|---|---|---|---|
| Sell-through | Units sold ÷ units received | How much of the buy has sold | Re-order and markdown decisions |
| GMROI | Gross margin ÷ average inventory at cost | Margin earned per unit of stock investment | Comparing brands and categories |
| Weeks of cover | Current stock ÷ average weekly sales | How long stock will last | Replenishment and allocation |
| Stock turn | Cost of goods sold ÷ average inventory at cost | How often stock is sold and replaced | Inventory efficiency |
| Markdown rate | Markdown value ÷ sales value | How much margin is given away in discounts | Pricing and buying quality |
How should these metrics be used together?
Each metric on its own can mislead. A high sell-through may simply mean the retailer bought too little. A strong GMROI may hide availability problems that cost sales. Low weeks of cover looks efficient until the style sells out mid-season.
- Sell-through with weeks of cover separates genuine winners, with high sell-through, low cover and plenty of season left, from styles that are simply running out.
- GMROI with markdown rate shows whether a strong return depends on full-price selling or on clearing stock cheaply.
- All metrics by size reveal whether a style's problem lies with the product or with the size curve bought.
- Net of returns for online sales, so the figures reflect what customers kept.
How do brands use retail metrics with their wholesale partners?
For brands selling wholesale, these metrics are the language of the buyer. A brand that can show strong sell-through and GMROI in a retailer's own stores has the best possible argument for more space and a larger order. Shared data on weeks of cover allows brands to propose timely replenishment and to plan production with fewer surprises.
The practical steps are straightforward: agree which metrics matter, exchange the underlying sales and stock data regularly, review them together during the season and use them to shape the next buy. Metrics that both sides trust turn a negotiation over order size into a joint plan for selling more product at full price.
Frequently asked questions
What is a good sell-through rate in fashion?
There is no universal benchmark, because targets depend on the category, price point, period measured and how sell-through is defined. Retailers set targets by category and season and compare styles against those internal benchmarks.
How is GMROI different from gross margin?
Gross margin shows profit on sales. GMROI relates that gross margin to the average investment in inventory at cost, so it also reflects how quickly stock turns and how much capital it ties up.
How do you calculate weeks of cover?
Divide current stock in units by average weekly sales in units, ideally using recent weeks. The result shows how many weeks the stock would last at the current rate of sale.
One edition every weekday morning. Read in five minutes. Free for industry professionals.
