Translate revenue into contribution before deciding what you can spend to acquire an order.
Revenue is only the beginning
Return on ad spend is a useful ratio: attributed revenue divided by advertising spend. It helps describe how much revenue a reporting system associates with the money you spent. It does not tell you how much of that revenue the business keeps.
Two stores can report the same ROAS and have very different outcomes. One sells a high-margin product with low fulfillment costs. The other pays more for the goods, subsidizes delivery, and receives more returns. The ratio is the same because none of those differences appears in its denominator.
Before setting a target, build a simple order-level account. Use consistent definitions, the same currency, and the same period. The calculation does not need to be elaborate. It needs to make the costs visible and avoid treating an attributed sale as automatic profit.
Walk through one order
Here is a fictional order, with every number stated explicitly. Revenue is after discounts, excludes sales tax, and is before the future return allowance shown below. The allowance represents expected losses not already deducted elsewhere.
| Item | Per order |
|---|---|
| Revenue | $100 |
| Product cost | −$40 |
| Delivery cost paid by the business | −$8 |
| Payment and transaction fees | −$3 |
| Expected return-loss allowance | −$4 |
| Contribution before advertising | $45 |
The $45 is not net profit. It is the amount left to cover advertising, fixed operating expenses, and the contribution the business wants to retain. If advertising costs $30 per acquired order, this example leaves $15 after advertising and before fixed overhead and tax.
Do not count the same loss twice. If your reported revenue is already net of refunds, the return allowance should cover only additional costs you have not included. Likewise, if a fulfillment charge already includes delivery, do not subtract shipping again. A precise-looking calculator cannot fix inconsistent inputs.
Derive the target instead of copying it
Assume each order is the first purchase by a newly acquired customer; cost per order then equals customer acquisition cost. In this simplified first-order model, the break-even acquisition cost is $45. At that point the order covers the listed variable costs and the advertising, leaving nothing toward fixed overhead. The corresponding revenue ROAS is $100 divided by $45, or about 2.22.
If the business wants to keep $15 per order after advertising, its acquisition-cost ceiling falls to $30. The corresponding target ROAS becomes $100 divided by $30, or about 3.33. The higher target comes from a business requirement, not a change in the advertising platform.
These are planning thresholds under the stated assumptions. They are not promises about what the market will deliver. If an achievable acquisition cost is above the ceiling, the options include improving the offer, changing costs, finding a different route to customers, or choosing not to run the campaign.
Be careful with blended averages
Average order values can hide an expensive mix change. A campaign might sell more low-margin bundles while the store’s overall margin is supported by a different product. Use the product mix associated with the decision where possible, or show several scenarios instead of one confident average.
The customer mix matters too. Revenue from existing customers does not answer exactly the same question as revenue from acquiring new ones. If your goal is new-customer growth, examine that group separately and define how you identify it. A returning customer may still be a valuable advertising outcome, but label it accurately.
Repeat purchasing can justify a different acquisition target when you have credible cohort evidence. Keep observed repeat contribution separate from an optimistic lifetime-value forecast. A business can run out of cash while waiting for a theoretical future margin. Show the payback period and cash requirements alongside any longer-term estimate.
Attribution and economics are different questions
An order can be profitable and still not have been caused by the ad. Conversely, an ad can influence a purchase that your chosen report does not attribute to it. The contribution model describes the economics of an order. Incrementality asks how outcomes change because advertising ran.
Keep both questions on the review agenda. Use the store’s records to understand orders and costs. Use advertising reports with their stated definitions. Where the spending decision is material and the setup permits it, consider a suitable lift or holdout study. Do not infer causality simply because a transaction appears inside an attribution window.
This distinction helps prevent two common overreactions: assuming every attributed sale is extra business, and dismissing all advertising because two dashboards disagree. First understand the accounting and measurement boundaries. Then choose a method that answers the question you actually have.
Use a range when the inputs are uncertain
If return losses are not yet known, compare a lower, middle, and higher allowance. If fulfillment costs differ by location, show the relevant cases. If you plan to raise spend, do not assume the next customer will cost the same as the average customer so far.
The ad economics calculator makes this arithmetic editable. It calculates contribution, acquisition-cost limits, and the corresponding ROAS from your inputs. It does not forecast demand or prove that a campaign caused a sale.
Bring the result back to an operating decision. What can this business afford to pay now? What contribution should remain? Which uncertain input could change that answer? Those three questions are more useful than asking whether a ROAS number looks impressive on its own.
About this article
Prepared by JDGMNT Editorial on 24 October 2026. Worked examples are illustrative; they are not campaign results or product benchmarks. The artwork was generated for this collection.