CAC (Customer Acquisition Cost)
The total cost of acquiring one new customer, including sales and marketing.
CAC is total sales and marketing spend in a period divided by new customers acquired in the same period. Blended CAC includes organic customers; paid CAC counts only those from paid channels.
Founders often quote blended CAC because it is lower, but investors ask for paid CAC. Blended looks better precisely when organic is doing the work, which does not scale with spend.
CAC is only meaningful against LTV and payback period. A high CAC is fine if customers stay for years; a low one is not enough if they leave in three months.