GMROI Calculator: Gross Margin Return on Inventory Investment
This GMROI calculator shows how much gross margin each unit of money invested in stock earned: gross margin divided by average inventory at cost. A GMROI of 1.5 means every 1 held in inventory returned 1.50 of gross margin over the period.
GMROI = gross margin ÷ average inventory at cost. Use the same period for both inputs.
The numbers stay in your browser and are not sent anywhere.
How to Use the GMROI Calculator
- Choose the period, usually a season or a rolling 12 months.
- Enter the gross margin for that period in money: net sales minus cost of goods sold.
- Enter the average inventory at cost over the same period.
- Read the GMROI and compare it between categories, brands or markets rather than on its own.
GMROI Formula and How to Read It
The second line shows why GMROI is useful: it combines margin and stock productivity in one number. A category can reach the same GMROI with a high margin and slow stock, or a lower margin and fast stock. A GMROI below 1 means the stock earned less gross margin than it cost to hold. My article on retail KPIs for fashion brands explains how GMROI sits next to stock turn, sell-through and margin in a weekly report.
GMROI Calculation Worked Example
Take two illustrative categories over the same year. Knitwear made a gross margin of 120,000 on an average inventory of 80,000 at cost, so its GMROI is 120,000 ÷ 80,000 = 1.5. Outerwear made 150,000 of gross margin but held 150,000 of stock on average, so its GMROI is 1.0. Outerwear earned more margin in total, yet knitwear used its stock money better. That is the conversation GMROI starts: whether the extra outerwear depth is worth the money tied up in it.
| Category | Gross margin | Average inventory at cost | GMROI |
|---|---|---|---|
| Knitwear | 120,000 | 80,000 | 1.5 |
| Outerwear | 150,000 | 150,000 | 1 |
Common Mistakes in GMROI Calculations
- Using inventory at retail price, which makes GMROI look lower than it is.
- Taking closing stock instead of average stock for the period.
- Mixing a quarterly gross margin with an annual average inventory.
- Using the margin percentage instead of gross margin in money.
- Ranking categories by GMROI without checking sell-through and availability.
GMROI Calculator FAQ
GMROI equals gross margin in money divided by average inventory at cost for the same period. A gross margin of 120,000 on an average inventory of 80,000 gives a GMROI of 1.5. It can also be written as gross margin percentage multiplied by sales-to-stock ratio.
Add up the category’s net sales minus cost of goods sold for the period to get gross margin. Average the category’s stock at cost over the same period, for example from month-end values. Divide the first figure by the second.
Above 1 means the stock earned more gross margin than it cost; beyond that, a good level depends on the category and business model. Compare categories within your own business and track the trend. A falling GMROI usually means stock is growing faster than margin.
Because GMROI measures the return on money invested in stock, and that money is the cost value. Inventory at retail price would include margin that has not been earned yet. The average smooths out seasonal peaks.
Related Retail Analytics Articles
How to Calculate Sell-Through Rate in Retail and Power BI
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Free Retail Calculators for Margin, Sell-Through and Stock
Sell-Through Rate Calculator
Sell-through on available stock and on receipts, with returns taken out of sales.
Margin Calculator
Gross margin, markup and gross profit from cost and price, plus the price you need for a target margin.
Stock Turn and Weeks of Cover Calculator
Stock turn, days of stock and weeks of cover from cost of goods sold, inventory and weekly sales.