A campaign showing 3.0 ROAS can still leave little money after product costs, delivery, payment fees and refunds. Before making a scaling decision, define which revenue and costs the ratio includes.
This guide uses an illustrative $100 order to calculate contribution before and after advertising. It is a planning model, not an accounting statement or a forecast. Download the contribution review worksheet and replace every example amount with consistent business records.
Start with one consistent revenue basis
Decide whether the revenue input already excludes discounts, refunded revenue and collected taxes. Keep that convention the same throughout the calculation. If refunds have already reduced net revenue, subtracting them again understates the result.
Shopify's profit report documentation explains that recorded product costs and discounts affect reported margin. A product gross-profit report is useful evidence, but the advertising decision also needs the additional costs relevant to the order.
For the example below, $100 is revenue after discounts and excluding tax, but before the illustrated refund allowance. We include product cost, variable fulfillment and payment costs, and the allowance separately. Fixed overhead and income taxes are outside this simplified model.
Calculate the amount available for advertising
| Item | Illustrative amount |
|---|---|
| Revenue on the stated basis | $100 |
| Product cost | $35 |
| Variable fulfillment and payment costs | $10 |
| Refund allowance not already deducted | $5 |
| Contribution before advertising | $50 |
The order leaves $50 before advertising: $100 minus $35 minus $10 minus $5. On this basis, contribution margin before advertising is 50% of revenue. Spending the full $50 to acquire this order would leave zero contribution toward the excluded costs.
The corresponding contribution break-even ROAS is $100 divided by $50, or 2.0. Equivalently, divide 1 by the contribution-margin fraction, 0.50. This is why a percentage must be converted to a fraction when using the formula directly.
Open the break-even ROAS calculator. Enter 100 as net order revenue and 50 as variable cost per order for this example. The tool returns 2.00 times break-even ROAS, $50 break-even CPA and a 50% contribution margin. Do not subtract the same fees or refund allowance a second time.
Distinguish break-even from a target
Suppose the business wants to retain $20 per order toward overhead and profit. In the example, only $30 of the $50 pre-ad contribution remains available for acquisition. The corresponding revenue-to-spend target is $100 divided by $30, approximately 3.33.
At a reported 3.0 ROAS, acquisition cost for the same $100 revenue basis would be about $33.33, leaving approximately $16.67 after the modeled variable costs and advertising. That clears the simplified contribution break-even point but misses the $20 retention goal.
Neither threshold tells you how much volume is available at that cost or whether the ad caused an incremental sale. It only expresses the economics under the stated assumptions. The ROAS calculator can reproduce the arithmetic for a larger batch of orders using its own labeled inputs.
Run a cost sensitivity check
Change one assumption at a time. If variable fulfillment and payment costs rise from $10 to $15, pre-ad contribution falls to $45 and contribution break-even ROAS rises to about 2.22. If revenue falls because of a discount, product cost may not fall with it.
Use separate rows for materially different products or markets. An average that combines a high-margin accessory with a low-margin bulky item can hide the economics of the product being advertised. Record the order mix and the period used to calculate any blended figure.
For refunds, use a consistent cohort and document what the allowance represents. A campaign's most recent orders may not have completed the normal return window. Treat unresolved returns as uncertainty rather than quietly assuming the refund rate is zero.
Reconcile platform attribution with business records
An advertising platform's attributed revenue is not automatically the same as store revenue for the period. Multiple platforms can claim credit for the same customer journey, and reporting windows can differ. Keep the attribution view useful without treating every platform total as additional revenue.
Use the MER calculator for a separate blended revenue-to-marketing-spend view, with its limitations stated. When reviewing Google Performance Max, the channel report workflow helps keep channel ratios and campaign totals consistent.
Before approving a budget change, record the revenue basis, costs included, target contribution, attribution window and review owner. Carry those assumptions into the creative test budget or a supported AdRails review. The campaign decision should remain tied to the economics you actually checked.
Source checked October 14, 2026. All values are illustrative; the model excludes fixed overhead, income taxes and any costs not explicitly entered.
