Customer Acquisition Cost, or CAC, answers a blunt question: how much did it cost to turn a stranger into a paying customer? It bundles the marketing and sales spend behind a group of new customers and divides it across them. For any publisher running paid growth, CAC is the line between scaling profitably and buying customers at a loss.

How to calculate CAC

CAC = Total acquisition spend / New customers acquired

CAC = Total acquisition spend / New customers acquired

CAC = Total acquisition spend / New customers acquired

Acquisition spend can be narrow, just media cost, or broad, folding in the tools, creative, and team time behind the campaign. Decide which costs you include and keep that definition consistent, because a CAC that quietly leaves out half the budget flatters the numbers.

A worked example

Say you spend $20,000 across a month of campaigns and gain 400 new paying customers:

$20,000 / 400 = $50 CAC

$20,000 / 400 = $50 CAC

$20,000 / 400 = $50 CAC

Each paying customer cost $50 to acquire. Whether that is good or bad depends entirely on what those customers are worth over their lifetime.

CAC vs. CPI

CAC is easy to confuse with CPI (Cost Per Install), but they count different things. CPI is the cost of a single install from any user, most of whom may never pay. CAC is the cost of an acquired, paying customer, and it can include broader sales and marketing costs beyond the install itself. A cheap CPI can still produce an expensive CAC if very few installs convert into customers.

Why CAC matters

CAC is only half a ratio. It has to be read against LTV (Lifetime Value), the total revenue a customer returns before they churn. The working rule is simple: CAC must sit well below LTV, and the wider the gap, the healthier the model. ROAS (Return On Ad Spend) and payback period describe the same relationship from other angles, showing how fast the spend earns itself back.

CAC also shapes how aggressively you can grow. When the gap between CAC and LTV is comfortable, you can spend more to acquire customers and still profit, so the ceiling on your growth is really the ceiling on how much value each customer returns. That is why teams work both levers at once: pushing CAC down through better targeting and creative, and pulling LTV up through retention and monetization. A campaign that looks expensive on CAC alone can be entirely sound once the value side of the equation is counted.

How offerwalls change the CAC math

Most CAC discussions assume a customer only pays you through purchases. An offerwall adds a second income stream: users earn rewards for completing offers, and the publisher earns from advertisers. That revenue raises the effective value of every user, including the many who never buy anything, which lifts LTV and lets a publisher profitably support a higher CAC. Earnings from RevU's offerwall can be reinvested into User Acquisition, funding growth from monetization the app already produces.

Common mistakes to avoid

• Treating CAC and CPI as the same number. One counts installs, the other counts paying customers, and the gap between them can be enormous.

• Leaving real costs out of the numerator so CAC looks lower than it truly is.

• Judging CAC without LTV. A $50 CAC is excellent for a customer worth $300 and ruinous for one worth $20.