Contribution Margin

The formula and a worked example

Contribution margin can be expressed in dollars (Revenue − Variable Costs) or as a ratio (Contribution Margin / Revenue). For a consulting project that bills \$10,000 and uses \$3,500 of contractor time and \$200 of pass-through expenses, contribution margin is \$6,300 (63%).

That \$6,300 is what's left to pay for the salaried staff, the office, the software stack — and, eventually, the owner's profit. Comparing contribution margins across customers, service lines, or pricing tiers tells you which work is genuinely funding the business.

Using it to drive decisions

Break-even sales = Fixed Costs / Contribution Margin Ratio. A business with \$50K/month of fixed costs and a 60% contribution margin needs \$83K of monthly revenue to break even. Any revenue above that drops 60 cents on the dollar to operating profit.

When deciding whether to take on low-priced work, the question isn't whether the price covers fully-loaded cost — it's whether contribution margin is positive. As long as fixed costs exist regardless, additional contribution margin is additional cash, even at lower-than-target margins.

Using contribution margin to make decisions

Contribution margin tells you whether a specific job, customer, or product line is paying for itself in the variable sense. A job with 20% contribution margin contributes 20 cents on every dollar of revenue toward fixed costs and profit. Two jobs with similar revenue but different contribution margins have very different effects on the business — the higher-margin one funds the team's salaries faster.

At the customer level, contribution margin reveals which relationships are creating cash and which are quietly destroying it. Calculate it including all variable costs of serving the customer — labor, materials, payment processing, customer success time, support tickets — not just the cost of goods sold. A surprising number of businesses discover that their largest customers are also their lowest-contribution-margin customers because of negotiated pricing concessions.

Contribution margin × volume = total contribution dollars, which is the number that has to cover fixed costs before any profit appears. Pricing decisions, product-mix shifts, and customer-firing decisions all flow from this math. Operators who internalize contribution margin tend to make much better trade-offs than those who only think in terms of gross margin or top-line revenue.

When the contribution margin of a customer or product line is structurally low (under 20% in a service business, under 40% in software), the question isn't whether to fix it — it's whether the business model itself is broken. Sometimes the right answer is to fire the customer, sunset the product, or fundamentally re-price; sometimes it's to accept a strategic loss leader. Either way, the contribution-margin number forces the conversation.