Three numbers on the same income statement are all called margin, and managers quote them interchangeably in the same meeting. Then they argue about a decision that was never actually in dispute, because each of the three answers a different question. Gross margin, contribution margin and net margin are not competing versions of the truth. They are three cuts through the same euro of revenue, and picking the wrong cut is how a product that looks profitable survives three budget cycles before anyone notices it never covered the cost of serving it.
What is the difference between gross margin, contribution margin and net margin?
Gross margin is revenue minus cost of goods sold, so it measures how efficiently you produce or deliver. Contribution margin is revenue minus all variable costs, including commissions, distribution and variable selling costs, so it measures what each additional sale contributes towards covering fixed costs. Net margin is what remains after every cost, fixed and variable, operating and financial. Gross margin classifies cost by function, contribution margin classifies it by behaviour, and net margin is the final answer.
Gross margin asks about production, not about profitability
Gross margin starts from revenue and subtracts cost of goods sold: materials, direct labour and the production or delivery overhead that accounting standards require you to attach to the product. It is the first line of the income statement that carries useful information, and it answers one question well: are we making or delivering this efficiently enough for the price we charge?
What it cannot tell you is whether the sale was worth making. Cost of goods sold is a functional bucket, defined by where the cost was incurred and not by whether it moves with volume. A supervisor on a fixed salary sits inside it; a sales commission does not. So two products with the same gross margin can behave in completely opposite ways when volume changes, and gross margin will not warn you.
Contribution margin asks whether the next sale is worth taking
Contribution margin re-cuts the same costs by behaviour instead of by function. Everything that rises and falls with the unit is variable: materials, piece-rate labour, freight, commission, transaction fees, packaging. Everything that stays put regardless of volume is fixed. Revenue minus variable cost is contribution, and the name is literal: it is the amount each sale contributes towards covering the fixed cost base and, once that base is covered, towards the result.
This is the only one of the three that answers an incremental question. Should we accept a one-off order below list price? Should we keep a product whose net margin is negative? Should we discount to win volume? None of those is settled by gross margin, because gross margin includes fixed cost that will be incurred either way, and none is settled by net margin, which in practice drags in even more allocated fixed cost.
Net margin is the number that has to survive everything
Net margin is revenue minus every cost: production, selling, administration, financing and tax. It is the number owners and lenders care about, and the only one that reconciles to the cash. It is also the least useful for a decision taken inside the business, precisely because it is complete. Every allocated fixed cost is in there, spread by whatever convention the accounting system uses, and that convention was designed for reporting, not for choosing.
That is where the trouble starts. When overhead is allocated on a broad-brush basis, usually revenue, headcount or direct labour, net margin per product or per customer becomes a function of the allocation rule as much as of reality. A cost-to-serve view exists precisely so that the allocation reflects the capacity actually consumed, and net margin per customer starts to mean something.
Gross margin tells you whether you make it well. Contribution margin tells you whether to sell it. Net margin tells you whether you survived the year.
Why the three disagree, and why that is useful
A product can carry a healthy gross margin and a thin contribution margin, because its selling and distribution costs are variable and sit below the gross margin line. A customer can show a strong contribution margin and a negative net margin, because it consumes a disproportionate amount of service, support and rework that no product-level view captures. These disagreements are not errors in the accounts. They are the accounts warning you that function and behaviour are different axes.
The practical move is to stop treating the three as a ranking and start reading them as a cascade. Revenue, then variable cost, then the directly attributable fixed cost, and only then the shared cost that someone genuinely has to carry. The margin cascade is the structure that makes each step visible, instead of collapsing them into a single percentage nobody can act on.
Which margin belongs in which decision
Use gross margin to compare production or delivery efficiency across products, plants and periods, and to talk to people outside the business who expect the standard statement. Use contribution margin for pricing, discounting, special orders, range rationalisation and break-even. Use net margin to judge the business as a whole and to confirm that the decisions taken on contribution actually left something behind.
One warning that costs companies real money: never drop a product because its net margin is negative without first checking its contribution margin. If contribution is positive, dropping it removes that contribution and leaves the fixed cost exactly where it was, so the remaining products absorb more overhead and the next report looks worse. It is the most common self-inflicted wound in cost management, and it comes entirely from reading the wrong margin.
The Profitability Health Check maps how your costs behave and where your margin really comes from, before you change a single price.