About the GMROI Calculator
This GMROI calculator measures gross margin return on inventory investment — how many dollars of gross margin you earn for every dollar tied up in inventory at cost. Enter net sales and cost of goods sold for a period, plus inventory at cost at the start and end of the period (or the same figure twice if you already have an average). You get GMROI, gross margin in dollars and percent, average inventory, inventory turnover and the sales-to-stock ratio.
Buyers, merchandise planners and store owners use GMROI to compare products, categories, vendors or stores on a single number that combines profitability and inventory productivity. A high-margin item that sits on the shelf can earn a lower GMROI than a modest-margin item that turns quickly.
Use the same period for sales, COGS and inventory. For an annual GMROI, use a year of sales and COGS and a year-average inventory; for a shorter period the result is for that period only. A GMROI above 1 means the inventory earned more gross margin than it cost to hold; many retailers look for well above that, varying by category.
With the default inputs, the gmroi is 2 x. Change any value above to recalculate instantly.
How to use the gmroi calculator
- 1Enter net sales for the period.
- 2Enter cost of goods sold for the same period.
- 3Enter inventory at cost at the beginning and end of the period.
- 4Read GMROI and compare it across products, categories or stores.
- 5Use margin % and turnover to see which lever to pull.
Formula and method
Gross margin is net sales minus the cost of the goods sold. GMROI divides that margin by the average amount invested in inventory, valued at cost, over the same period. Average inventory here is the simple average of beginning and ending inventory; if you track monthly balances, a 13-point monthly average is more accurate and can be entered in both fields.
GMROI can be decomposed into gross margin percentage multiplied by the sales-to-stock ratio (sales ÷ average inventory at cost), which shows the two levers: price and margin on one side, inventory productivity on the other. Inventory turnover (COGS ÷ average inventory) and days of inventory are shown for context.
- Net sales
- Sales after returns and discounts
- COGS
- Cost of goods sold in the same period
- Average inventory
- Average inventory value at cost
Worked examples
Annual GMROI for a specialty store
Gross margin is $500,000 − $300,000 = $200,000 and average inventory ($90,000 + $110,000) ÷ 2 = $100,000, so GMROI is 2.0: each $1 of inventory earned $2 of gross margin. That is 40% margin × 5.0 sales-to-stock.
High-margin, slow-turning jewelry
A 55% margin produces $132,000 of gross margin, but $160,000 of average stock gives GMROI of only 0.83 because inventory turns just 0.68 times a year.
Low-margin, fast-turning grocery category
Only a 25% margin, but $60,000 of average inventory turns 15 times, so GMROI is $300,000 ÷ $60,000 = 5.0 — far better than the jewelry example.
Frequently asked questions
What is GMROI?+
GMROI (gross margin return on inventory investment) is gross margin divided by average inventory at cost. It tells you how many dollars of gross margin each dollar invested in inventory produced over a period, usually a year.
What is a good GMROI?+
Above 1 means the inventory returned more gross margin than its cost. Many retailers look for considerably higher figures, but benchmarks vary widely by category: fast-moving consumables can reach high GMROI on thin margins, while furniture or jewelry run lower.
How do I improve GMROI?+
Raise gross margin through better pricing, buying and fewer markdowns, or reduce average inventory by buying shallower, reordering more often and clearing slow movers. Both levers multiply together, so small gains in each add up.
Should inventory be at cost or retail for GMROI?+
Standard GMROI uses average inventory at cost, because that is the money you actually invested. Some retailers calculate a variant with inventory at retail; that produces a lower number and is not comparable with the cost-based figure.
What is the difference between GMROI and inventory turnover?+
Inventory turnover (COGS ÷ average inventory) measures only how fast stock moves. GMROI adds profitability by using gross margin instead of COGS, so it rewards both turning inventory quickly and earning a good margin on it.