Every founder eventually has to answer the same question: how many units do I need to sell to stop losing money? Break-even analysis — the oldest technique in managerial accounting — gives the answer in a single formula. It also exposes which businesses are structurally profitable, which are one bad month from insolvency, and which will never scale no matter how much revenue they generate. Understanding contribution margin is the difference between running a business and being run by it.

The core formula is elegant: Break-Even Units = Fixed Costs ÷ Contribution Margin per Unit. Contribution margin is price minus variable cost — the amount each sale contributes toward covering fixed costs and, beyond that, generating profit. A $100 product with $30 of variable cost has a $70 contribution margin and a 70% CM ratio. With $70,000 of monthly fixed costs, you need 1,000 units per month to break even. Sell 1,500 and you make $35,000 profit. Sell 500 and you lose $35,000.

Contribution margin varies enormously by industry, and this alone predicts whether a business can scale. SaaS software: 80–95% because marginal cost of one more subscription is nearly zero. Consulting: 60–80% depending on labour intensity. E-commerce brands: 40–60% after shipping and payment fees. Restaurants: 25–35%. Grocery: 10–20%. Below 20%, small cost shocks or price cuts wipe out profit — the business runs on volume and has almost no room for error.

Cost-Volume-Profit (CVP) analysis extends break-even into planning. Adding a target profit is trivial: Units for Target = (Fixed Costs + Target Profit) ÷ Contribution Margin. Want $50k monthly profit on the example above? Sell 1,714 units instead of 1,000. This directly translates strategic goals into weekly sales targets — the foundation of every rational operating plan.

Margin of safety measures how much revenue can fall before you start losing money. Actual sales of 1,500 units vs a 1,000-unit break-even is a 33% margin of safety — the business can absorb a one-third revenue drop before hitting red. Under 20% is risky (any recession or churn wave kills profitability). Over 40% is comfortable. Investors and lenders always ask this number even when they don't call it by name.

The biggest strategic mistake in break-even math is confusing revenue with contribution. A 10% price cut with unchanged costs doesn't just cut profit 10% — it can double the units needed to break even because contribution margin shrinks disproportionately. A product with 30% CM that cuts price 10% now has 22% CM (a 27% CM drop). To make the same total contribution you now need 37% more units. Always model price changes with this calculator before promising 'we'll make it up on volume' — most of the time, you won't. Use this alongside our Profit Margin, Markup and ROI calculators for a full unit-economics analysis, and export the model as PDF or CSV for board and investor conversations.