Paid sales and marketing spend divided only by the customers acquired through paid channels; isolates the true cost of bought growth.
New-customer CAC, also called paid or new CAC, divides paid sales and marketing spend by the customers acquired through paid efforts only. Wall Street Prep treats this as a distinct variant from blended CAC: new CAC counts only customers won through paid efforts, while blended CAC counts everyone (wallstreetprep.com).
This is the figure that tells you whether the paid acquisition engine itself is economical. By excluding organic and word-of-mouth customers, who carry near-zero marginal cost, it stops free demand from flattering the paid channels you are actively scaling.
Worked example (Demonstrative): A$120,000 of paid spend acquiring 400 paid new customers gives a new-customer CAC of A$300. If those customers carry an A$900 contribution-margin LTV, the paid engine runs at a 3.0:1 LTV:CAC, a healthy ratio. Read against blended CAC of A$200 you would have overstated the paid engine's efficiency.
Blufire compares new-customer CAC to break-even ROAS and MER and to LTV computed on contribution-margin dollars, so the cost of bought growth is judged against the profit those customers actually generate, not against revenue or a blended average.