GMROIGross Margin Return on Inventory Investment

GMROI stands for Gross Margin Return on Inventory Investment. It measures how much gross profit a SKU (or category) generates for every pound of average inventory held.

It's the single best metric for ranking SKU performance because it combines two things that matter — margin and velocity — into one comparable number.

A SKU with high margin but slow turnover can have the same GMROI as a low-margin fast-mover. The metric makes them visible alongside each other.

The formula

GMROI = Gross profit / Average inventory cost

Or equivalently:

GMROI = Gross margin % × Inventory turnover

The second form makes the structure explicit. GMROI = how much margin you make per unit × how many times you sell through your inventory in a year.

Worked example

A SKU sold £100,000 over the year at 50% gross margin (£50,000 gross profit). Average inventory at cost was £20,000.

GMROI = £50,000 / £20,000 = 2.5

That tells you: every £1 of inventory investment generated £2.50 of gross profit over the year.

Cross-check via the alternative form:

• Gross margin = 50% (i.e. 0.50)
• COGS = £50,000 (sales of £100,000 − gross profit of £50,000)
• Inventory turnover = COGS / Avg inventory = £50,000 / £20,000 = 2.5
• Wait — gross margin × turnover should give GMROI. 0.50 × 2.5 = 1.25, not 2.5.

The discrepancy comes from a definitional subtlety. Some references calculate "gross margin" relative to sales (the standard accounting definition); others use a "markup" relative to cost. The two forms are equivalent if defined consistently:

• GMROI = Gross profit / Avg inventory cost (the cleanest form, used here)
• = (Gross margin % on sales) × (Sales / Avg inventory cost)
• = 0.50 × (£100,000 / £20,000) = 0.50 × 5 = 2.5 ✓

Stick with the gross-profit-divided-by-average-inventory form. It's unambiguous.

What "good" looks like

Healthy GMROI varies by category, but the general bands:

• GMROI < 1.0 → losing money relative to inventory investment; usually need to fix margin, fix sell-through, or stop ranging
• GMROI 1.0–2.0 → marginal; needs attention, not necessarily action
• GMROI 2.0–4.0 → healthy for most consumer brands
• GMROI > 4.0 → strong; usually high-margin or fast-moving SKUs (often both)

Industry benchmarks for total business GMROI:

• Specialty retail: 2.5–4.0
• Beauty / wellness: 3.0–5.0
• Apparel: 2.0–3.5
• Hard goods / electronics: 1.5–2.5
• Grocery: 5.0+

Why GMROI beats margin alone or turnover alone

Margin alone misses velocity. A 70%-margin SKU that sells 20 units a year is dead capital.

Turnover alone misses profitability. A 4× turnover on a SKU sold at 5% margin makes pennies per pound invested.

GMROI combines them. The ranking it produces is the most operationally useful one for buying and ranging decisions:

• Top GMROI SKUs → reorder, expand, allocate display
• Bottom GMROI SKUs → mark down, discontinue, reduce reorder quantities

GMROI by category, channel, and supplier

The metric scales:

• By category — which categories deserve more inventory investment
• By channel — D2C GMROI vs wholesale GMROI vs marketplace GMROI; the same SKU can have wildly different GMROI per channel
• By supplier — which suppliers' SKUs work hardest for the inventory investment

A common pattern: D2C GMROI is usually the highest (full margin, owned audience). Wholesale GMROI is lower (margin compressed) but turnover often higher. Marketplace GMROI varies most because of variable fees.

Common pitfalls

• Using selling price instead of cost for "average inventory." Inventory is held at cost on the balance sheet; the formula uses that. Using selling price inflates GMROI artificially.
• Annualising too aggressively. GMROI is most stable over a 12-month rolling window. Quarterly GMROI bounces around with seasonality and isn't comparable across periods.
• Comparing GMROI across categories without context. A grocery brand running GMROI of 5 and a furniture brand running GMROI of 1.5 might both be healthy for their categories.

GMROI vs other inventory metrics

Where GMROI fits in the metric stack:

• Inventory turnover — speed of sell-through, agnostic to margin
• Sell-through rate — % of a batch sold in a window
• GMROI — combines margin and turnover into one number; the ranking metric

For ranking SKUs by inventory productivity, GMROI is the metric to use.