Define the metrics before comparing them
Return on ad spend is attributed revenue divided by ad spend. Customer acquisition cost is the acquisition spending you include divided by new customers acquired. State whether CAC includes only paid media or also creative, software, team and sales costs.
A platform ROAS and a business-level CAC answer different questions. The platform describes what it attributes under its measurement rules. Your business records describe customers and revenue actually received. Use both, but do not combine unlike definitions into one dashboard headline.
Separate new customers from repeat purchases
A campaign can report strong revenue because existing customers return. That may be commercially valuable, but it does not prove that new-customer acquisition is efficient. Separate new and returning customer revenue wherever your records support it.
Watch brand search, remarketing and retention campaigns in particular. Their role is different from reaching people who have never heard of the business. Evaluate the incremental contribution of each motion instead of giving all revenue credit to the final ad interaction.
Use contribution margin to interpret ROAS
Revenue is not the money available to fund marketing. Subtract variable costs such as product cost, fulfillment, fees and expected returns to estimate contribution before advertising. Keep tax treatment and revenue recognition consistent with your own accounting definition.
Illustrative example: 10,000 in attributed revenue from 2,000 in ad spend produces 5× ROAS. If contribution before ads is only 20% of that revenue, advertising consumes the entire 2,000 contribution before fixed overhead. The same 5× ROAS could look very different for a product with a higher contribution margin.
Watch payback and cohort maturity
For a subscription product, the timing of gross profit matters. CAC payback asks how long it takes cumulative customer gross profit to cover acquisition cost. A simple calculation can be useful, but cohort retention and changing plans may require a more detailed model.
Do not assume a new customer will stay forever because early churn is low. Recent cohorts have not had time to demonstrate long-term retention. Use conservative scenarios for planning and update them as evidence arrives. Growth that looks attractive on lifetime value can still put pressure on cash flow.
Build a weekly decision table
Put spend, new customers, paid-media CAC, collected revenue and contribution after advertising on one consistent time basis. Add lead quality or activation when the business has a longer buying journey. Flag measurement gaps instead of silently filling them with assumptions.
Ask whether a channel is producing suitable new customers, whether its economics are improving and whether the team can absorb more volume. Scale only when those answers support it. If the platform and business reports disagree, investigate attribution windows, refunds, duplicate events and customer definitions before moving large budgets.
Quick reference
| Metric | What it describes |
|---|---|
| ROAS | Attributed revenue relative to advertising spend. |
| Paid-media CAC | Media spend per new customer. |
| Fully loaded CAC | Included sales and marketing costs per new customer. |
| Contribution after ads | Revenue left after specified variable costs and advertising. |
| CAC payback | Time for customer gross profit to cover acquisition cost. |
Try this next
Add a definition beside every acquisition metric, then calculate contribution after advertising for one product or customer cohort.
Further reading: Official documentation.
Turn this guide into a working brief
- Write down the business question and the metric that would answer it.
- Choose one change you can isolate and explain why it should help.
- Decide who owns the work, how it will be measured and when to review it.