Stop optimising ROAS. Start optimising blended CAC.
Channel-level return on ad spend is the most confidently reported wrong number in Indian marketing. Here is what it hides and what to use instead.
· 7 min read · Paid Media
Every platform reports the conversions it can claim. Meta claims them on a seven-day click and one-day view. Google claims them on a data-driven model it will not show you. Your own analytics claims them on last non-direct click. Add the three together and you will routinely find you sold 140% of what you actually sold.
This is not fraud. Each platform is answering a narrow question honestly. The problem is that nobody is answering the question the business actually has, which is: for every rupee that left the bank this month, how much new revenue arrived?
What blended CAC actually is
Take everything you spent on acquiring customers in a period — media, agency fees, tools, the salary of the person running it — and divide it by the number of new customers you acquired in that period. No attribution model, no lookback window, no platform-reported anything. It is a number your finance team can verify from the bank statement and the CRM.
If a channel cannot survive being measured this way, it was probably never working.
What changes when you switch
- Retargeting stops looking like your best channel. It was taking credit for buyers who were already coming.
- Brand search stops looking like a hero. Most of those people typed your name because something else worked.
- Upper-funnel spend that looked wasteful starts to justify itself, because it is what fed the two above.
- The argument about which platform gets the credit disappears, because none of them do.
How to run it without a data team
A spreadsheet is enough to start. One row per week. Columns for total acquisition cost, new customers, and blended CAC. Add a column for total revenue and one for contribution margin after cost of goods. Six weeks of that will tell you more than a year of platform dashboards.
The discipline that makes it work is the holdout. Turn a channel off for two weeks in one region and watch what happens to total new customers. If nothing happens, you found your answer, and it will be uncomfortable.
The honest caveat
Blended CAC is a lagging aggregate. It will not tell you which creative to kill on Tuesday. You still need channel-level data for daily operations. The point is which number governs the budget decision, and that should be the blended one.
