Customer acquisition cost, or CAC, captures how much a company spends on average to win a new customer. It is computed by dividing total sales and marketing spend by the number of new customers gained in the same period, which forces the question of whether each acquired customer is genuinely worth the money spent to attract them. CAC is most useful when paired with lifetime value, or LTV, which estimates the total gross profit a customer will generate over the entire relationship with the business. Comparing LTV to CAC, often written as \( \text{LTV:CAC} \), reveals whether the underlying economics support continued investment in growth.
Payback period adds a time dimension to this comparison by measuring how many months it takes to recover the cost of acquiring a customer from that customer's gross profit. A short payback period means a startup can reinvest quickly, while a long payback period signals that growth is being financed by ever-deeper cash reserves. Unit economics is the broader framing in which all of these numbers sit: it asks whether revenue and costs at the per-customer or per-transaction level can ever produce a profitable whole. A classic mistake is to scale acquisition aggressively before the unit economics actually work; growing into a losing proposition simply makes losses arrive faster.
Closely related is the break-even point, the moment when revenue finally covers costs. Break-even is a milestone, not a strategy, but it helps founders understand how much funding they need and how realistic their runway assumption is. Confusing revenue growth with profitability is easy when both are rising at once, but until the break-even line is crossed, growth is still consuming cash. Looking at unit economics, payback period, and break-even together turns growth from a hopeful story into a calculable plan.