How to Track Which Inventory Lines Are Actually Profitable
- Retailers carrying unprofitable inventory lose an average of 11% of potential profit annually
- The four costs that determine true inventory profitability
- How to calculate profit per SKU
- Inventory turn rate and its relationship to profitability
- What to do with your profitability data once you have it
- Building a monthly inventory profitability review into your operations
Most inventory analyses stop at revenue. True inventory profitability requires tracking cost of goods, carrying cost, return rate, and fulfilment cost at the SKU level. This post shows how to build that view and what to do with it.
- Retailers carrying unprofitable inventory lose an average of 11% of potential profit annually
- The four costs that determine true inventory profitability
- How to calculate profit per SKU
- Inventory turn rate and its relationship to profitability
- What to do with your profitability data once you have it
Retailers carrying unprofitable inventory lose an average of 11% of potential profit annually#
That figure, from a 2024 retail profitability study, reflects a problem that is almost universal in small retail and eCommerce businesses: stock is purchased based on what sells, not what profits. The distinction matters because selling a product at a 40% markup sounds healthy until you account for the 15% return rate, the storage cost for the six weeks it sits before selling, the customer service overhead from complaints, and the discount required to clear end-of-season stock. Net of those costs, the 40% markup becomes a 6% margin. Meanwhile, a product moving half the volume with a 60% markup and a 3% return rate delivers three times the profit per pound invested. Most operators do not know which of their products sit in which category.
The four costs that determine true inventory profitability#
True profitability at the SKU level requires accounting for four cost categories beyond the purchase price. First, landed cost: the purchase price plus import duties, shipping, and any quality inspection costs. For imported goods, this can add 15 to 35% to the purchase price and is frequently underestimated. Second, carrying cost: the cost of having stock sitting in your warehouse or fulfilment centre, typically calculated at 20 to 30% of inventory value per year. A product that takes 60 days to sell carries significantly higher cost than one that turns in 15 days. Third, return cost: processing a return typically costs 15 to 25% of the sale price in labour and restocking. Fourth, fulfilment cost: pick, pack, and ship per unit, which varies significantly by size and weight.
How to calculate profit per SKU#
For each SKU, the calculation is: revenue minus landed cost minus carrying cost during average days-to-sell minus (return rate multiplied by return processing cost) minus fulfilment cost per unit. The result is your true gross profit per unit. Multiply by units sold in a period to get total profit contribution per SKU. Rank all your SKUs by this number. The top 20% by profit contribution are your core lines — protect them, ensure consistent stock availability, and consider whether you can expand into adjacent products with similar unit economics. The bottom 20% are your candidates for discontinuation, repricing, or supplier renegotiation. Most operators are surprised by which products appear at the bottom. It is rarely the ones they expected.
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Inventory turn rate and its relationship to profitability#
Inventory turn rate — the number of times you sell through your average inventory in a year — is the most important secondary metric for understanding profitability. A product with a 30% margin that turns 12 times per year delivers more profit than a product with a 50% margin that turns twice. This is because each day a product sits unsold, carrying costs are accumulating against it. Calculate turn rate for each SKU by dividing annual units sold by average units held in stock. For most retail categories, a turn rate below 4 is a warning sign. Below 2, the product is almost certainly unprofitable on a fully-loaded basis even if its gross margin looks healthy. High turn rate combined with acceptable margin is the combination to prioritise in your buying decisions.
What to do with your profitability data once you have it#
Once you have ranked your SKUs by true profitability, three actions follow. First, stop reordering consistently unprofitable lines. This sounds obvious but is harder in practice — operators often have emotional attachment to products they launched with, or relationships with suppliers that make discontinuation feel awkward. The data makes the conversation easier. Second, renegotiate landed costs on your highest-volume unprofitable lines before discontinuing them. A 10% cost reduction from a supplier can turn a marginal line into a profitable one. Third, redirect your marketing budget toward your most profitable SKUs. Many operators spend their advertising budget on their highest-volume products, not their highest-margin ones. Shifting spend to high-margin products can increase total profitability without increasing revenue.
Building a monthly inventory profitability review into your operations#
Inventory profitability is not static. A product that was profitable six months ago may have become unprofitable due to a supplier price increase, a rise in return rates, or a new competitor undercutting your selling price. A monthly review — which should take no more than 30 minutes once you have built your initial profitability model — flags these changes before they compound. Connect your inventory management system and your accounting software to keep landed costs current. Review the bottom quartile of your SKU profitability list every month. The products that appear there consistently over three months are the candidates for removal. Products that newly appear warrant investigation — something changed in their cost structure or return behaviour that needs to be understood and addressed.
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