The Ecomm Analyst

Channel CAC is a number I used to put on every monthly report. Meta CAC at $42. Google CAC at $28. TikTok CAC at $51. Tidy. Easy to talk about. Almost entirely useless for actual decisions.

The math falls apart because every channel is computing CAC against attributed conversions, and the attributed conversions overlap. If Meta and Google both claim the same customer, both their CACs look better than reality. Add up the new customers each platform claims and you get more new customers than you actually acquired.

Blended CAC sidesteps the whole argument. Total paid spend divided by total new customers acquired. One number, no attribution debate. If I spent $40k on ads last month and acquired 800 new customers, blended CAC is $50. Doesn’t matter which platform claims credit. The bank account doesn’t care.

The objection I get is that blended CAC doesn’t tell you where to allocate. Fair. It tells you whether your overall acquisition economics are working, which is a different question and arguably the more important one.

For allocation, I use blended CAC as the ceiling and look at directional channel signals to test against it. If blended CAC is trending up while Meta spend is also up and other channels are flat, Meta is probably the cause. Not certain. Probably. That’s enough to test by pulling spend down on Meta and watching what happens to blended CAC over the next two weeks.

This is where independent attribution helps without being trusted as gospel. ThoughtMetric gives me a survey-weighted and multi-touch view that I treat as a tiebreaker, not a verdict. The blended number is what I commit to in the operator review. The attribution view is what I use to form a hypothesis about why it moved.

If you only have time to track one acquisition number in your weekly review, make it blended CAC. Channel CACs will have you defending budget allocations that are mathematically impossible. Blended CAC will have you talking about whether the business is actually working.