Most ecommerce operators know their revenue by product. Far fewer know their profit by product. The gap between those two numbers is where margin quietly disappears — sometimes for years before anyone notices.
SKU-level profitability analysis answers a deceptively simple question: after every variable cost is accounted for, which products are actually making money? The answer is almost always surprising. Research across 50 ecommerce brands found that an average of 62% of SKUs were unprofitable when all costs were properly allocated. The top 25% of SKUs generated roughly 85% of total contribution margin. The catalog looked healthy at the revenue line; it looked very different at the contribution line.
This guide covers why revenue is the wrong lens, how to calculate true SKU-level contribution margin, which costs operators consistently miss, and how to act decisively once you have the data.
Why Revenue by SKU Is Misleading
Revenue is a popularity contest. The products that generate the most revenue are the ones customers buy most often, at the highest volume, driven by the most marketing spend. None of that tells you whether selling those products is a good use of your capital.
Consider a $60 apparel item with a 50% gross margin. On paper, $30 of gross profit per unit looks solid. But layer in outbound fulfillment ($8), return processing on a 35% return rate ($4.50 expected cost per unit sold), payment processing ($1.80), and size-specific storage costs for slow-moving variants, and that $30 can shrink to $12 or less — well below what the revenue rank would imply.
Gross margin makes this problem worse, not better. Standard gross margin typically includes supplier cost and sometimes inbound freight but excludes fulfillment, returns, and channel fees. The result is a margin figure that looks healthy but does not reflect what the product actually nets out at when it ships to a customer and — sometimes — comes back.
The 80/20 pattern in ecommerce profitability is persistent and predictable. Roughly 20% of SKUs generate 80% or more of contribution margin. The question is not whether this is true for your catalog — it almost certainly is — but which 20% it is and what you are going to do about the other 80%.
How to Calculate SKU-Level Contribution Margin
The formula is straightforward. The data work is where most operators get stuck.
The Core Formula
SKU Contribution Margin = Net Revenue per Unit − Variable Costs per Unit
Net revenue is selling price minus discounts and refunds. Variable costs include every cost that moves when one more unit ships. Fixed costs — warehouse rent, headcount, software — are allocated separately and do not belong in per-SKU contribution margin.
Building the Variable Cost Stack
Work through the cost stack in the order costs are incurred:
1. Landed COGS. Start with the supplier unit cost and add every cost required to get the product to your warehouse: inbound freight (air or ocean), import duties and customs fees, port handling and brokerage, insurance in transit, and any inbound inspection fees. For internationally sourced goods, landed cost typically runs 15–30% above the base supplier unit price. Distributing these costs across units using weight or cubic volume ratios gives the most accurate per-SKU figure.
2. Warehousing and storage. Allocate storage cost by SKU based on cubic volume and dwell time. A large, slow-moving SKU that sits in a fulfillment center for 90 days consumes far more capital than a compact, fast-turning SKU. Many operators skip this step and are surprised to find that their lower-velocity SKUs are materially more expensive to hold than their blended storage rate suggests.
3. Pick, pack, and outbound fulfillment. Third-party logistics (3PL) providers charge per-unit pick-and-pack fees, dimensional weight shipping, and carrier surcharges. For a standard apparel item, total outbound fulfillment typically runs $6–12 depending on weight, dimensions, carrier zone, and whether the SKU ships with inserts or special packaging. If you use your own warehouse, this is labor cost per pick plus materials.
4. Payment processing and platform fees. Stripe, Shopify Payments, and other processors typically charge 2.5–3% plus a flat transaction fee. For a $40 item, that is $1.20–$1.40 per sale, which compounds quickly across high-volume SKUs.
5. Returns allocation. This is the most frequently omitted cost. The average ecommerce return rate is 20–25% industry-wide; apparel runs 25–40%. Each return incurs reverse logistics ($6–15), inspection and restocking labor ($3–8), and repackaging materials. To get a per-unit cost, calculate your return rate for each SKU and multiply by the average cost per return. A 30% return rate at $12 average return cost adds $3.60 to the effective cost of every unit sold.
6. Channel and marketplace fees. If the SKU sells on Amazon, eBay, or another marketplace, referral fees (typically 8–15% of selling price depending on category) apply. These need to be tracked per channel, not blended across the catalog, since the same SKU may have very different economics on DTC versus Amazon.
What to Produce
The output of this calculation is a contribution margin per unit and a contribution margin percentage for each SKU. You want to rank your catalog by total contribution dollars (not percentage), because a 40% margin SKU that sells 10 units a month is less important than a 22% margin SKU that moves 500 units. Percentage tells you efficiency; dollars tell you scale.
Common Costs Operators Miss
Even operators who do some SKU-level analysis routinely leave costs out. The most common omissions:
Size and Variant Imbalance
A single parent SKU in apparel might have 12 size and color variants. Some sell fast; some accumulate in the warehouse for months. When operators average costs across the parent, slow-moving variants are subsidized by fast-moving ones. Breaking down to the variant level often reveals that XS and 3XL in a given colorway are losing money while the core sizes are profitable.
Return Rate Variance by SKU
Return rates are almost never uniform across a catalog. A sizing-inconsistent apparel SKU might return at 40%; a basic accessory might return at 5%. Spreading a blended return rate across all SKUs masks the damage done by high-return products. Per-SKU return rates should be tracked and applied individually.
Dimensional Weight Surcharges
Carriers calculate shipping cost as the greater of actual weight and dimensional weight. A product that is light but bulky — foam products, large-format packaging, home goods — often triggers dimensional weight pricing that makes outbound shipping 30–50% more expensive than the product's actual weight would suggest. If you are using a blended per-order shipping cost in your SKU model, you are almost certainly undercosting bulky SKUs.
Hazmat and Special Handling
SKUs that fall under hazmat classifications (certain electronics, batteries, aerosols, some beauty products) incur surcharges at 3PLs and with carriers. These costs are sometimes absorbed at the warehouse level and not passed through to SKU-level cost reports, making affected products appear more profitable than they are.
Inbound Freight Volatility
Freight costs fluctuate significantly. A landed cost model built on 2022 freight rates understates costs for any inventory purchased during high-freight periods, and overstates costs for inventory sourced after rates normalized. Landed cost should be updated at the purchase order level, not held as a static figure in the product master.
How to Act on SKU Profitability Data
Having accurate per-SKU contribution margin data is useful only if it drives decisions. There are four primary actions.
Discontinue
Discontinuation is the right answer when a SKU has a negative contribution margin with no realistic path to profitability, carries meaningful inventory that is tieing up working capital, and has a high return rate or fragile demand. The test is not whether revenue will drop — it will — but whether contribution margin increases. A catalog that generates $5M in revenue at a 12% contribution margin is worse than a catalog that generates $4M in revenue at an 18% contribution margin. The objective is contribution dollars, not revenue.
Before discontinuing, run the inventory out rather than writing it down where possible. Consider liquidation channels, clearance pricing, or donation if the carrying cost of holding it exceeds the expected recovery. Tools like Fairview can model the contribution impact of removing specific SKUs from your active catalog and project how overall margin evolves as you rationalize.
Reprice
Repricing is the right first move when a SKU has a genuine customer base, the margin gap is modest, and competitive positioning allows for a price increase. A SKU running at 8% contribution margin because it is priced $4 below the market may simply need a price correction.
When repricing, be precise about the elasticity. For commodity or comparison-shopped products, even a small price increase can meaningfully reduce conversion. For proprietary or branded products, customers are often less sensitive than operators assume. Test a 5–10% increase on a subset of traffic before committing to a full price change.
Also consider channel-specific pricing. A SKU that loses money on Amazon due to referral fees may be profitable on DTC at the same price. Shifting the channel mix — through search, email, or bundle placement — can improve blended contribution without changing the product at all.
Bundle
Bundling pairs a low-margin SKU with a high-margin one to improve blended economics. If a $30 accessory runs at 45% contribution margin and a $25 add-on runs at 8%, a $50 bundle (discounted from $55) at a blended 28% contribution margin may net more dollars per transaction than selling the accessory alone.
Bundling also helps address slow-moving variants. A size or color that is not moving on its own may move well when paired with a fast-moving complementary item. This reduces inventory carrying cost while improving the economics of the high-margin SKU by increasing its attachment rate.
Restructure the Cost
Sometimes the right action is not a pricing or catalog decision but a cost renegotiation. If a SKU's contribution margin is negative primarily because of inbound freight — particularly relevant for heavy or bulky items sourced internationally — it may be worth exploring nearshore sourcing, smaller and more frequent purchase orders (which reduce carrying cost), or a different fulfillment model (dropship versus warehouse stock).
Platforms like Fairview give operators a clear view of which cost component is the primary driver of margin compression for each SKU. When you can see that a specific SKU's problem is a 38% return rate rather than product cost, the corrective action is different — better sizing guides, improved product photography, more accurate size charts — than if the problem is inbound freight.
Putting It Into Practice
SKU-level profitability analysis is not a one-time exercise. Costs change with every purchase order, every freight rate revision, and every shift in return behavior. A product that was marginally profitable last quarter may be unprofitable today because ocean freight rates moved or a carrier added a surcharge.
The operational discipline is to maintain a live contribution margin model — updated at the PO level for landed cost, at the weekly level for return rates, and at the monthly level for fulfillment rates — and to review the SKU ranking quarterly as a standing agenda item with buying, operations, and finance together.
Most ecommerce operators run their catalog decisions on revenue rank and gut feel. The ones who run on contribution margin per SKU tend to carry leaner catalogs, turn inventory faster, and grow more predictable profit — not because they are selling more, but because they know exactly what they are selling and what it is worth.
Fairview surfaces contribution margin by SKU, variant, and channel in a single view — pulling landed cost, fulfillment data, return rates, and channel fees into one model so operators have the decision-ready data they need without building it manually in spreadsheets.