Margin, ROAS and Break-Even: Read the Denominator First

A number can be calculated correctly and still answer the wrong question. Revenue divided by advertising spend answers a different question from profit divided by revenue. Before comparing ratios, write down the numerator, denominator and reporting period.

Margin uses revenue

Suppose a sale produces revenue of 100 and includes costs of 80. The difference is 20. The Margin Calculator divides that difference by revenue: 20 / 100 × 100 = 20%.

Markup uses cost instead: 20 / 80 × 100 = 25%. A 20% margin and a 25% markup can describe the same sale. They should not be substituted for each other when setting a price.

The result includes only the costs entered. If 80 covers product cost but omits delivery and overhead, the resulting 20 is not automatically net profit. Use the same cost scope when comparing periods. Revenue of zero makes the margin ratio undefined; the calculator reports an error rather than displaying a misleading zero.

ROAS uses advertising spend

With attributed revenue of 3000 and ad spend of 1000, the ROAS Calculator returns 3×. Each unit of advertising spend corresponds to three units of attributed revenue in the selected window.

The calculation does not subtract inventory, delivery, refunds or any other costs. It also cannot determine whether the attribution model assigned revenue correctly. Compare the same currency and attribution window, and keep the original platform definitions beside an exported result.

Simple ROI has different arithmetic. A total return of 1500 on an investment of 1000 gives (1500 − 1000) / 1000 × 100 = 50%. The return field means the total recovered value, including the original investment. Entering only the gain would answer a different question.

Break-even uses contribution per unit

Assume fixed costs of 1000, selling price of 20 and variable cost of 10 per unit. Each unit contributes 10 toward fixed costs. The Break-Even Calculator returns 100 units and revenue of 2000.

If price equals variable cost, contribution is zero. Selling additional units cannot cover positive fixed costs under that model. If variable cost exceeds price, additional sales increase the shortfall. Those cases should not produce a normal positive break-even quantity.

A fractional threshold needs interpretation: 100.2 units means at least 101 when only whole units can be sold. The underlying model assumes constant unit price and cost; volume discounts or capacity changes require updating the inputs.

Save only what you intend to keep

These tools keep inputs in page memory and provide an explicit Copy result action. Calculating does not put amounts into a sharing URL. Copy the output together with its period, currency and cost definitions into your own record before leaving the page.

The worked values above are arithmetic checks used by the project. They are not revenue forecasts or promises that a particular advertising return is sufficient for a business.