Contribution Margin: Formula and Examples

Contribution margin is what each sale leaves after its variable costs — the money that pays for fixed costs first and becomes profit after that. It is the number behind every break-even calculation.

Two ways to express it

Per unit it is a dollar amount: $50 − $30 = $20. As a ratio it is the share of every sales dollar that goes toward fixed costs: $20 ÷ $50 = 40%. The ratio is useful when you sell many products at different prices, or when you think in revenue rather than units.

Contribution margin vs gross margin

Gross margin subtracts the cost of the goods sold; contribution margin subtracts the costs that vary with sales, such as payment fees, shipping you pay and sales commissions. The two are not the same number, and contribution margin is the one that belongs in break-even math.

Break-even revenue from the ratio

Divide fixed costs by the ratio: $10,000 ÷ 0.40 = $25,000 of revenue. It is the same answer as 500 units at $50, reached without counting units.

Total contribution for a period

Multiply the unit figure by the units sold and you have the total contribution of a period — the amount available for fixed costs. Selling 800 units of the $50 item gives $16,000. Laid out as a contribution-format income statement, the month reads as follows.

Using the ratio for a change in sales

Because fixed costs do not move with volume, the contribution margin ratio tells you how profit reacts to sales. At 40%, every extra $1,000 of sales adds $400 to operating income, and every $1,000 lost removes $400. If sales in the month above drop 15% to $34,000, contribution falls to $13,600 and operating income to $3,600 — a 40% fall in profit from a 15% fall in sales. The shortcut assumes the price, the variable cost per unit and the sales mix stay the same; a discount changes the ratio itself and needs a fresh calculation. For several products, use the weighted ratio of the actual sales mix rather than the ratio of any single item.

Frequently asked questions