Direct Answer
Customer acquisition cost (CAC) is the total marketing and sales spend required to acquire one new customer over a defined period (typically a month or quarter). Calculate as (marketing + sales spend) / new customers. Track blended CAC across all channels and per-channel CAC by source. Healthy CAC is one-third of LTV or less.
Short version
“Customer acquisition cost is total marketing and sales spend divided by new customers. Healthy CAC is one third of lifetime value or less.”
Per-channel CAC tells you where to scale and where to cut. Blended CAC alone hides high-CAC channels behind low-CAC ones.
Track CAC payback period — months until LTV exceeds CAC. Under 12 months is excellent for service businesses.