Months to Recover CAC Calculator

CAC payback answers a cash question rather than a profit question: how many months of gross profit from one customer are needed to return the money spent winning that customer. Gross profit is used instead of revenue because hosting, support and third-party software must be paid before anything is left to repay acquisition; software gross margins usually sit between 65 and 85 percent, so a 200 dollar subscription at 80 percent margin contributes 160 dollars a month toward recovery. A fully loaded acquisition cost includes sales salaries and commissions, marketing spend and tooling, onboarding effort, and the infrastructure cost of trials that never convert. Understating any of these produces a flattering payback figure. The conventional reading places anything under six months as excellent, six to twelve as good, twelve to eighteen as tolerable where contracts are annual and churn is low, and beyond eighteen as a signal that pricing, margin or acquisition efficiency needs work. Churn changes the shape of the answer, and the churn-adjusted figure shown here is the more honest one. Because each month only a surviving fraction of the cohort still pays, cumulative gross profit converges rather than growing without limit: at a constant monthly churn rate the total ever recoverable per customer is monthly gross profit divided by that churn rate. At 2 percent monthly churn and 160 dollars of monthly gross profit, no acquisition cost above roughly 8,000 dollars is ever repaid on average, no matter how long the horizon. This is why payback and the lifetime value to acquisition cost ratio must be read together, and why the model here stops searching at 120 months. The calculation also assumes flat pricing and constant churn, so it ignores expansion revenue, discounting, seasonality, and the cash advantage of prepaid annual contracts.

The payback period itself is a standard capital budgeting tool, taught for decades as a rough screen for how quickly an investment returns its outlay before more sophisticated discounted cash flow measures are applied. Its migration into subscription software followed the recognition that acquiring a customer is a capital expenditure with a deferred return, not an expense matched to the period in which it occurs. Under perpetual licensing the question barely arose, because the licence fee arrived up front; once revenue was spread across months, the mismatch between immediate sales cost and gradual collection became the central financing problem of the business model. The metric was codified around 2010. Bessemer Venture Partners set out its Ten Laws of Cloud Computing in that year, arguing that a healthy cloud business should recover customer acquisition cost within about twelve months, and David Skok published the SaaS Metrics 2.0 framework in the same period, which explicitly named months to recover CAC alongside the lifetime value to acquisition cost ratio and popularised the pairing. Both drew on the cash lessons of the 2008 to 2009 downturn, when growth-at-any-cost companies found funding unavailable before their cohorts had repaid. The metric became prominent again from 2022, when rising interest rates made capital expensive and boards shifted their primary test from growth rate to efficiency, with payback period and the related burn multiple the usual instruments.