Define both measures explicitly
For ROAS, identify the revenue source, attribution rule and media cost. For an ROI view, explain which contribution or profit measure is used and which marketing costs are subtracted. Avoid counting the same cost twice.
Neither formula resolves causality on its own. If the revenue is attributed rather than proven incremental, describe the result accordingly.
Compare the questions
| Measure | Main question |
|---|---|
| ROAS | How much credited revenue is reported per unit of ad spend? |
| Contribution after marketing | What remains after the stated variable and marketing costs? |
| Defined marketing ROI | What economic return is calculated relative to the included investment? |
| Incremental return | What additional value did the intervention create under a credible comparison? |
Build a useful report
- Separate revenue from contribution.
- Include relevant variable costs and adjustments.
- State the acquisition or marketing cost scope.
- Account for customer outcome timing.
- Distinguish observed credit from causal impact.
A different cost definition may be appropriate for a different decision. The problem is changing the definition silently or comparing unlike measures.
Worked example: show the formulas
Illustrative example: 100 units of advertising spend is credited with 500 units of revenue. Reported ROAS is 500 / 100 = 5. If contribution before that advertising cost is 160 units, contribution after the spend is 60. An ROI defined as post-ad contribution divided by ad investment is 60 / 100 = 60%.
That example includes only the stated advertising cost. Adding production or other marketing costs would change the economic calculation, and attributed revenue still does not prove added impact.
Keep customer quality visible
Returns, refused delivery, discounts and support costs can alter the apparent return. Use mature operational outcomes when possible. A campaign that attracts unsuitable buyers can look strong before those later costs appear.
Is a target ROAS enough to manage a business?
No. It is one input. Contribution, cash timing, customer value and capacity also matter.
Which ROI formula is correct?
Use a definition suited to the decision and document it. Consult the appropriate finance owner for material reporting or investment decisions.
Put this into practice
Write your ROAS and ROI formulas beside the report, identify the revenue and cost sources and remove any comparison that uses inconsistent scopes.
Primary-source reading for platform details: Google Ads: conversion tracking.
Related foundation: CAC vs ROAS: which metric should guide your marketing budget?. How these guides are prepared.
Ayoub Mouhachtt
Growth & performance marketing. Explore the portfolio and working background.
Related portfolio work: Etsy & Shopify. The worked examples in this guide are illustrative and are separate from the portfolio’s project evidence.