Blended CAC vs Paid CAC: What's the Difference?

Blended CAC divides total acquisition spend by every new customer acquired in a period, regardless of channel - including organic, referral, email, and word-of-mouth customers who cost little or nothing to convert, alongside the ones brought in through paid spend.

Paid CAC divides only paid acquisition spend by the customers actually attributed to paid channels, isolating how efficiently paid marketing specifically is converting spend into customers.

The gap between the two can be large, and it's specifically the free, low-cost customers pooled into blended CAC that create it - paid CAC has been observed running roughly two to three times higher than blended CAC across many categories, because blended CAC spreads paid spend's cost across a denominator that includes customers who cost nothing to acquire. That makes blended CAC misleading if it's the only number watched: a strong brand pulling in plenty of organic and returning customers can make paid acquisition look cheap in the blended number even while the paid channel itself is becoming genuinely expensive and inefficient underneath it. Blended CAC still has real value as the truest top-line read on overall go-to-market efficiency - it's what actually reflects total spend against total customers acquired - while paid CAC is the more useful number specifically for judging and optimizing individual paid campaigns, which is why tracking only one of the two leaves a real blind spot on the other side of the acquisition picture.