The single number that says whether your unit economics work — lifetime value against acquisition cost, plus payback period.
Divide a customer's lifetime value by what it costs to acquire them. A result of 3:1 means each $1 spent on acquisition returns $3 of lifetime value. If you also know the monthly gross profit a customer generates, CAC payback = CAC ÷ monthly gross profit per customer tells you how many months it takes to earn the acquisition cost back.
A customer is worth $900 in lifetime value and costs $300 to acquire. LTV:CAC = 900 ÷ 300 = 3:1 — right on the healthy benchmark. If that customer throws off $50 of gross profit a month, CAC payback = 300 ÷ 50 = 6 months.
The rule of thumb is 3:1, with 3:1 to 5:1 considered healthy. Below 1:1 you lose money on every customer you acquire — the model is unsustainable. Between 1:1 and 3:1, acquisition is expensive relative to the value you capture and margins are thin. A ratio well above 5:1 looks great but often means you're underspending: you could acquire more profitable customers and are leaving growth on the table. Feed this with a margin-based LTV calculator figure and an honest CAC calculator number, and be sure the CAC is your fully-loaded cost, not just media spend.
What is a good LTV:CAC ratio? Around 3:1 to 5:1. Below 3:1 is expensive; below 1:1 loses money; far above 5:1 can signal underinvestment in growth.
What does a 3:1 ratio mean? A customer's lifetime value is three times the cost to acquire them — for example $900 LTV against $300 CAC.
What is CAC payback? Months to recover acquisition cost, calculated as CAC ÷ monthly gross profit per customer. Shorter payback frees cash to reinvest.
