Blended CAC (blended customer acquisition cost)

Blended CAC divides total sales and marketing spend by the total number of new customers acquired in a period, calculated as blended CAC = total spend / total new customers, without separating which channel each customer came through. It counts customers who arrived through organic search, referrals, or word of mouth in the denominator even though no direct spend produced them.

This is the key difference from a channel-specific cost per acquisition, which measures how efficiently one paid channel converts, and from paid CAC, a narrower variant some teams calculate using only paid spend and only customers attributed to paid channels. Blended CAC is generally lower than paid CAC precisely because it spreads the same total spend across a larger customer count that includes free acquisition. It is closely related to marketing efficiency ratio, which expresses a similar blended, channel-agnostic view in terms of revenue rather than customer count.

Blended CAC matters because it is harder to distort with attribution disputes between channels, and it is the figure most often paired with customer lifetime value in the LTV:CAC ratio used to judge whether a growth model is sustainable. Its main limitation mirrors that of any blended metric: it cannot say which channel is driving efficiency and which is dragging on it, so a healthy blended number can still hide an unprofitable paid channel subsidized by strong organic growth.