Contribution margin is the part of each sale that’s left after variable costs — the money that goes toward your fixed costs and then your profit. It’s the engine behind break-even analysis.
Contribution margin = Sale price − Variable cost per unit
Expressed as a percentage of the sale price, it becomes the contribution margin ratio — contribution margin ÷ sale price. The ratio is handy because it tells you what fraction of every extra dollar of sales drops through to cover fixed costs and profit.
Contribution margin isolates the effect of one more sale. Because fixed costs don’t change when you sell an extra unit, the contribution margin is exactly what that unit adds to your bottom line. That makes it the right tool for decisions like:
That last one is direct: break-even units = fixed costs ÷ contribution margin. See how to calculate break-even point for the full method, and fixed vs variable costs to classify your costs correctly first.
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Contribution margin is the money left from a sale after variable costs, which then contributes toward covering fixed costs and, beyond that, profit. Per unit it's the sale price minus the variable cost per unit.
Contribution margin per unit = sale price − variable cost per unit. The contribution margin ratio = contribution margin ÷ sale price, expressed as a percentage. For a $20 item with $8 of variable cost, the contribution margin is $12 and the ratio is 60%.
Gross profit subtracts all cost of goods sold, including some fixed production costs. Contribution margin subtracts only variable costs. The distinction matters for decisions like pricing a one-off order, because only variable costs change with that extra unit.
Break-even units = fixed costs ÷ contribution margin per unit. Contribution margin is literally the denominator of the break-even formula, so a higher contribution margin means you break even on fewer sales.
A higher contribution margin gives you more to cover fixed costs and more profit per sale, so it's generally better. But it must be weighed against volume — a lower margin on far higher volume can still win. Look at total contribution, not just the per-unit figure.