Once your GA4 data is accurate, the real work starts: turning it into a clear picture of what your marketing is actually returning. This toolkit covers the core formulas and reports to calculate ROI with confidence.
The Core ROI Formula
Marketing ROI equals (Revenue from marketing minus Marketing cost) divided by Marketing cost, shown as a percentage. To use this formula, you need two numbers from GA4: how much revenue or lead value came from each channel, and what you spent to get it.
Assigning Value To Leads
- Calculate your average deal size from closed sales
- Calculate your lead to close rate from your CRM
- Multiply average deal size by close rate to get an estimated value per lead
- Set this value on your key events in GA4 so lead value shows up in reports
Reports To Use
- Traffic acquisition report, to see which channels bring visitors
- Conversions report, to see which channels bring key events
- Google Ads campaign report, to see cost against key events for paid traffic
- Attribution report, to understand which touchpoints contribute to a sale
Putting It Together
- Pull channel level cost from your ad platforms and any agency fees
- Pull channel level revenue or lead value from GA4
- Calculate ROI per channel using the formula above
- Review this monthly to decide where to increase or reduce spend
Frequently Asked Questions
What if I do not know my exact close rate?
Start with your best estimate from recent sales history. An estimated lead value is far more useful than no lead value at all, and you can refine it over time.
Why does my Google Ads ROI look different in GA4 versus the Ads platform?
GA4 and Google Ads sometimes use different attribution models, so they can count credit for a conversion differently. Pick one source as your primary reference and use the other for context.
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