Calculate contribution dollars and ratio
Pre-ad contribution = net revenue − variable non-ad costs. Divide contribution by net revenue to get the contribution margin ratio; multiply by 100 for a percentage. This tool uses a paid-acquisition planning definition that excludes advertising from the cost input so the remaining amount can be tested as an acquisition allowance. It is not net profit.
Enter matching per-order averages from one cohort. The tool shows contribution dollars, contribution margin percentage and a simplified break-even ROAS using the same net-revenue basis. To understand how product accounting differs from this acquisition model, use the gross-margin versus contribution-margin comparison. Do not subtract a cost twice merely because it appears in more than one report.
Contribution margin (%) = (R − V) ÷ R × 100. Net-revenue break-even ROAS = R ÷ (R − V), only when contribution is positive. R is net revenue and V is variable non-ad cost on the same basis.
What belongs in each input?
| Input | Use | Avoid |
|---|---|---|
| Net revenue per order | Sales after discounts and refunds on your stated cohort basis | List price before a promotion, or taxes collected for a government |
| Variable non-ad cost per order | Product cost and relevant variable fulfillment, fees, packaging, shipping subsidy and return handling | Advertising, duplicated refunds, or allocated fixed overhead mixed into an incremental-order model |
Whether a cost varies is a business-specific question. Include the portion that changes with the order under the decision being modeled; document mixed or step costs rather than assuming every expense is fully variable. If shipping collected from customers is included in revenue, include the corresponding shipping cost consistently. Use one currency and the same order population for both inputs.
For 200 completed orders with $18,000 net revenue and $8,200 variable non-ad costs, enter $90 and $41: divide both totals by the same 200 orders. Alternatively the formulas work on matching period totals, but the fields and explanations here are labeled per order. Do not enter a period revenue total beside a single order's cost. Keep enough precision in your working records; display rounding does not change the underlying calculation.
Worked refund-adjusted order: $49 contribution
Assume a hypothetical cohort averages $100 in tracked order revenue, with $10 refunded, leaving $90 realized net revenue per acquired order. Variable non-ad costs are $30 net product cost, $6 fulfillment and shipping subsidy, $3 processing fees and $2 additional return handling. Total costs are $41. These inputs demonstrate the method, not industry benchmarks.
Enter $90 revenue and $41 costs. Contribution is $90 − $41 = $49. Contribution margin is $49 ÷ $90 × 100 = 54.44%. Spending the full $49 on acquisition gives a net-revenue break-even ROAS of $90 ÷ $49 = 1.84x. That leaves zero after-ad contribution for fixed costs or profit, so break-even is not a comfortable operating target.
The $10 refund already reduced revenue. Do not also include it in the $41 variable costs. Include actual net return-related costs separately, accounting for inventory recovery where relevant; do not charge full product cost twice for resalable returned stock. Choose a mature enough cohort for returns, or label a sensitivity case when outcomes remain uncertain.
Use the same revenue basis in the ROAS numerator
The same $49 allowance against $100 tracked revenue implies $100 ÷ $49 = 2.04x, not 1.84x. These are two revenue numerators for the same underlying economics. The calculator's ratio uses the net revenue you entered; it does not reconcile your ad platform automatically. Match it to a dashboard that uses the same refunds, taxes, attribution window, currency and order cohort.
If you need to keep $15 per order after advertising, the allowance is $49 − $15 = $34. Use the maximum CPA calculator for that reserve decision. The matching net-revenue target is $90 ÷ $34 = 2.65x; on the $100 tracked basis it is 2.94x. The target ROAS calculator then helps express a positive acquisition allowance as a target. These are economic checks, not guaranteed auction prices or automated bid recommendations.
Interpret zero, negative and unusually high results
| Result | Meaning in this model | Next check |
|---|---|---|
| Positive contribution | Some room remains before advertising | Reserve money for overhead and profit before setting CPA |
| Zero contribution | No positive first-order media allowance | Check pricing and cost scope; no finite break-even ROAS is shown |
| Negative contribution | Variable costs already exceed net revenue | Review order economics before treating more acquisition as a fix |
| Zero revenue | Contribution dollars still equal revenue minus costs | Margin ratio is undefined; do not turn it into a 0% claim |
A high percentage is not automatically a good business outcome: $10 revenue with $2 variable cost gives 80% contribution but only $8 before acquisition. Compare dollars and percentage together. A recurring business may use a validated longer payback model, but this first-order tool does not include lifetime revenue or predict retention.
Do not average product percentages blindly
Suppose basket A has $100 revenue and $50 contribution while basket B has $20 revenue and $2 contribution. The simple average of 50% and 10% is 30%, but pooled contribution is $52 ÷ $120 = 43.33%. Use total contribution divided by total comparable revenue. A changing basket mix can move the overall ratio even when each product's economics are unchanged.
For an advertising scenario based on a representative order, a $34 acquisition allowance and a 2% click-to-order rate imply $0.68 per click. Test that relationship in the maximum CPC scenario calculator using the matching traffic denominator. A conversion rate from sessions is not automatically interchangeable with an ad-click rate.
Keep a reusable cost worksheet
Record the cohort dates, revenue basis, cost categories, return assumptions and desired reserve in the free ROAS Profitability Workbook. Revisit this calculator after a fee, fulfillment, price or return-rate change, then update the acquisition target. Download access does not require marketing consent; optional messages remain a separate choice.
OpenStax's managerial-accounting reference below describes the general contribution and ratio framework. Our pre-ad ROAS interpretation is a stated planning adaptation, not an accounting classification rule. Check your cost mapping with finance before making spending decisions; platform-attributed revenue alone does not establish incremental profit.
Frequently asked questions
What is the contribution margin formula?
Contribution equals revenue minus variable costs. Contribution margin percentage equals contribution divided by revenue times 100. This tool excludes advertising from variable costs to show a pre-ad acquisition allowance.
Should I enter advertising in the variable-cost field?
No. This tool calculates contribution before advertising. Including ads here and then using the result as an acquisition allowance would subtract advertising twice.
Can contribution margin be negative?
Yes. When variable costs exceed net revenue, contribution is negative before advertising. No positive first-order media allowance or finite break-even ROAS exists in that case.
What happens when revenue is zero?
The tool still shows contribution dollars, but the contribution margin ratio and break-even ROAS are unavailable. A zero denominator is not a valid percentage.
Does this result equal net profit?
No. Advertising, fixed overhead and other excluded expenses still need to be considered. Positive pre-ad contribution does not establish overall business profitability.
Why can my platform's break-even ROAS differ?
The platform may use tracked revenue before refunds while this tool uses entered net revenue. Keep the same contribution dollars and match the revenue numerator before comparing ratios.
Reference
OpenStax: contribution dollars, ratio and total contribution. Reviewed October 16, 2026. Examples on this page are hypothetical and calculated independently.