Contribution Margin: The Number Behind Every Pricing Decision
- The definition, briefly
- Decision one: the special order
- Decision two: which product to push when capacity is short
- Decision three: dropping a product that “makes a loss”
- Where contribution thinking goes wrong
- Where this fits
Contribution margin is what each sale leaves after paying the costs that sale itself caused. It is the right number for almost every short-term pricing and product decision, because it ignores costs that stay the same whatever you decide. Full cost, which spreads rent and salaries across every unit, is useful for long-run pricing and for the accounts, but it gives the wrong answer to “should I take this order?” more often than owners expect.
The definition, briefly
Contribution per unit = selling price − variable cost per unit.
Variable cost is everything that rises with one more unit: materials, piece-rate labour, packaging, freight out, sales commission, payment fees. Fixed costs, such as rent, salaried staff and insurance, are left out because selling one more unit does not change them.
Contribution first covers fixed costs. Whatever is left after that is profit. The same idea drives break-even analysis; this article uses it for decisions.
Decision one: the special order
A small manufacturer makes a steel bracket.
| Per unit | ₹ |
|---|---|
| Normal selling price | 500 |
| Variable cost | 300 |
| Contribution | 200 |
| Fixed cost allocated per unit, at normal volume | 120 |
| Full cost per unit | 420 |
A new customer offers to buy 2,000 brackets at ₹380 each. The factory has spare capacity: the machines are idle for part of every week.
On full cost the order looks like a loss of ₹40 a unit, ₹80,000 in total. Most owners would decline.
On contribution it adds ₹380 − ₹300 = ₹80 a unit, ₹1,60,000 of extra profit. The ₹120 of fixed cost per unit is not caused by the order. Rent and salaries will be paid whether the brackets are made or not, so they do not belong in the decision.
Three conditions have to hold for that answer to be right:
- The capacity really is spare. If the 2,000 units would displace sales at ₹500, each displaced unit costs ₹200 of contribution to gain ₹80. The order then loses ₹120 a unit.
- No extra fixed cost is needed. An overtime shift, a new die or an extra supervisor turns part of “fixed” into a cost of this order.
- Existing customers will not learn the price. If regular buyers demand ₹380 too, the order has cost far more than it earned.
Decision two: which product to push when capacity is short
The same factory also makes a larger bracket. Both run on the same machines, and machine time is now the constraint: there are 4,000 hours a month.
| Small bracket | Large bracket | |
|---|---|---|
| Price | ₹500 | ₹800 |
| Variable cost | ₹300 | ₹560 |
| Contribution per unit | ₹200 | ₹240 |
| Machine hours per unit | 2 | 3 |
| Contribution per machine hour | ₹100 | ₹80 |
The large bracket earns more per unit, so it looks like the one to push. But it uses 50% more of the scarce resource. Filled entirely with small brackets, 4,000 hours earn ₹4,00,000. Filled with large brackets, they earn ₹3,20,000.
When something limits output, rank products by contribution per unit of the constraint, not per unit sold. The constraint may be machine hours, skilled labour, a material in short supply, shelf space or delivery slots. Whatever it is, divide contribution by it.
In practice you rarely drop a product entirely: customers want both, and demand for the better product runs out. The rule tells you which to make first and which to ration.
Decision three: dropping a product that “makes a loss”
A product line shows a loss in the management accounts after its share of overheads. Should it go?
Ask what disappears if it does. If the line brings in ₹6 lakh of contribution a year and carries ₹8 lakh of allocated overhead, it shows a ₹2 lakh loss. But if dropping it removes only ₹1 lakh of genuinely avoidable cost, a part-time packer and some storage, the business loses ₹6 lakh of contribution to save ₹1 lakh. Profit falls by ₹5 lakh.
The allocated overhead does not vanish. It gets reallocated to the remaining lines, which now look worse. This is how businesses cut their way into losses one “unprofitable” product at a time.
The line is worth dropping only if its contribution is less than the costs that would actually go away, or if the capacity it frees can earn more elsewhere.
Where contribution thinking goes wrong
Every price cannot be set at contribution. Special orders at marginal prices are fine at the edges. If most of your sales are priced just above variable cost, nothing is left to pay fixed costs. Long-run pricing has to recover full cost plus a margin.
Fixed costs are fixed only within a range. Double output and you need a second shift, a bigger premises or more staff. Decisions that change the scale of the business need the fixed costs back in the calculation.
Misclassified costs corrupt the answer. If a cost that rises with volume has been treated as fixed, contribution is overstated and marginal orders look better than they are. Classifying costs carefully is covered in fixed or variable: classifying costs from a real ledger.
Where this fits
- What a discount does to contribution: what a 10% discount really costs your margin
- How many units cover fixed costs: break-even analysis
- Check the arithmetic: profit margin calculator · break-even calculator
- Setting the base price: how to price a service business