Contribution margin
Also known as: contribution to fixed costs
Contribution margin is sales revenue minus variable costs. It shows how much of each sales dollar is left over to cover fixed costs and, once those are covered, to become profit.
Contribution margin isolates the part of revenue that actually responds to selling one more unit. The formula is contribution margin = sales revenue − variable costs. On a per-unit basis it is the selling price minus the variable cost per unit, and expressed as a percentage of sales it becomes the contribution margin ratio. Fixed costs are deliberately excluded, because they do not change with volume in the short run.
A worked example makes the mechanics clear. Suppose a product sells for $50 and costs $30 per unit in materials, direct labor, and variable overhead. The unit contribution margin is $20 and the contribution margin ratio is 40%. If fixed costs run $200,000 per period, the company must sell 10,000 units ($200,000 ÷ $20) to break even. Every unit beyond that adds $20 straight to operating income.
Because it separates cost behavior from cost function, contribution margin supports decisions that gross margin cannot. Managers use it for break-even and target-profit analysis, for deciding whether to accept a special order priced below full cost, for ranking products when a resource such as machine time is constrained, and for evaluating segments. A segment with a positive contribution margin is helping cover common fixed costs even if it shows a loss after allocations — which is why dropping it can make total profit worse.
Contribution margin sits at the center of the CMA Part 1 exam. Expect questions on contribution margin analysis in operational budgeting, on segment and responsibility-center reporting where controllable contribution margin is distinguished from segment margin, and on variable (direct) costing income statements, which report contribution margin instead of gross profit.
Key takeaways
- Contribution margin equals sales revenue minus variable costs; fixed costs are excluded on purpose.
- Unit contribution margin is price minus variable cost per unit; the contribution margin ratio expresses it as a percentage of sales.
- Break-even units equal fixed costs divided by the unit contribution margin.
- It drives special-order pricing, constrained-resource product ranking, and keep-or-drop segment decisions.
- Variable costing income statements report contribution margin, while absorption costing reports gross profit.