Customer acquisition cost
Customer acquisition cost (CAC) is the total amount a company spends on sales and marketing to acquire one new paying customer, calculated by dividing total acquisition spend over a period by the number of new customers gained in that period. It is one of the foundational unit economics metrics for any customer-facing business.
CAC is used to evaluate the efficiency of growth spending and, when paired with revenue and retention metrics, to assess whether the business model is financially sustainable. A company that spends more to acquire customers than it earns from them over time cannot scale profitably.
How customer acquisition cost is calculated
The standard formula is:
CAC = Total acquisition spend / Number of new customers acquired
Acquisition spend includes all costs directly tied to attracting and converting new customers: paid advertising, content production, sales team compensation and tools, events, and any channel-specific costs. The time period used, typically a month or quarter, should match between the numerator and denominator to avoid distortion.
One common calculation error is using total marketing and sales spend when only a portion of that spend is directed at new customer acquisition. Companies that invest in retention campaigns, upsell programs, or existing-customer marketing should isolate new-acquisition spend for an accurate CAC figure.
Why customer acquisition cost matters for customer experience
The relationship between CAC and customer lifetime value (LTV) sets the structural logic for how much a company can invest in customer experience. If acquiring a customer costs $200 and they generate $800 in lifetime revenue, there is a reasonable margin to invest in support quality, onboarding, and retention. If the LTV-to-CAC ratio is close to 1:1, the economics leave little room for service investment.
Customer experience also influences CAC indirectly. Companies with strong support reputations benefit from referrals and positive word of mouth, which reduce average acquisition cost over time. Conversely, poor experiences drive up customer churn rate, which forces the company to acquire more customers just to maintain revenue, effectively raising the effective CAC burden.
CAC, retention, and the cost of support
There is a direct economic argument for investing in support quality rooted in CAC logic: retaining a customer is nearly always cheaper than acquiring a new one. When support quality is high, customer retention rate improves, which reduces the volume of replacement acquisition spending needed. This is why support cost metrics like cost-per-resolution and deflection rate are worth tracking alongside growth metrics like CAC.
AI-powered support reduces cost-per-resolution while maintaining or improving response quality, which improves the retention side of the equation without requiring additional headcount. Teams that can demonstrate a link between support investment and reduced churn are in a strong position to justify AI tooling on financial grounds. Salesforce's overview of CAC benchmarks provides useful context on industry norms. Decagon's post on the value of self-serve support also illustrates how deflection strategies reduce the effective cost of serving the existing customer base.
For a deeper dive, download Decagon's report on AI and the next generation of customer experience.
