CAC · LTV
Customer Acquisition Cost / Lifetime Value
What is CAC?
- CAC = cost of acquiring one customer
- LTV = the total value a customer delivers
- LTV ÷ CAC ≥ 3 means a healthy business
Once you start using CAC and LTV, the language of your marketing meetings changes. 'This campaign generated 300 leads' becomes 'It cost KRW 9 million (≈ US$6,730) to win one client, and that client leaves us KRW 30 million (≈ US$22,400) in profit over three years.' Budgets are reallocated based on profit and loss per customer, not cost per impression or click count, and decisions such as hiring one more salesperson or taking a booth at a trade show are measured against the same yardstick.
Where you draw the boundary of the calculation determines how far you can trust the numbers. If you put only ad spend in the CAC numerator, you get about half the real figure. Include sales salaries, content production, travel, and free-trial operating costs. Blended CAC, which divides total marketing and sales spend by the number of new customers, and paid CAC, which looks at paid advertising alone, serve different purposes, so track them separately. The most common LTV method multiplies annual contract value by gross margin and divides by the annual churn rate. The numerator has to be profit, not revenue.
Before the ratio, look at the payback period. An LTV/CAC of 3x is conventional wisdom in the SaaS industry, but you also need to check whether CAC is recovered within 12 months, or cash runs dry. Mixing segments makes both numbers wrong. Large-enterprise customers have a CAC three to four times higher, but an even higher LTV, while small-business customers are cheap to acquire, yet half of them leave within a year. Lumping everything into one average leads you to cut the channels you should keep.
The most common mistake is calculating LTV from revenue. A ratio that looked like 3x drops to 1.5x when recalculated on profit. Many companies in their second year also inflate LTV by assuming customers will stay “five years on average” when they have no churn data yet. The opposite error is fixating on cutting CAC, which lowers lead quality and drags renewal rates down with it. A typical pattern: profit looks good for two or three months after ads are cut, then the pipeline dries up six months later and the sales team sits idle. If the ratio goes above 10x, don't read it as doing well. Read it as a sign you are under-investing in growth.
John KimInstructor John Kim, author of B2B Marketing Design and CEO of Nanum Consulting
Euijung KimBrand strategist with 30 years in advertising, formerly a division head at Daehong CommunicationsIt isn't a theory with a single founder. As subscription and SaaS businesses spread, it became a core unit-economics metric that weighs the cost of winning one customer against the total value that customer brings.
Let's look at a hypothetical case: Company A, a B2B online training platform with 35 employees and KRW 4.8 billion (≈ US$3,591,200) in annual revenue. Over two years its clients grew from 40 to 68, yet its operating margin fell from 9% to 4%. The CEO asked, 'Revenue is growing, so why is cash getting tighter?' and told the marketing team to pull six months of numbers again.
- The head of marketing added up every cost for the six months. Ad spend of KRW 180 million (≈ US$134,700) plus KRW 120 million (≈ US$89,800) in pay for three salespeople came to KRW 300 million (≈ US$224,500). Divided by 28 new client companies, CAC came out to KRW 10.71 million (≈ US$8,010).
- The finance director objected, saying, “Don’t call annual contract value of KRW 12 million (≈ US$8,980) the LTV.” Factoring in a 62% gross margin and a 78% annual renewal rate, LTV came to about KRW 33.8 (≈ US$1) million, and LTV/CAC was 3.2x.
- The problem was payback. Each customer generated KRW 7.44 million (≈ US$5,570) in annual profit, so it took 17 months to recover a CAC of KRW 10.71 million (≈ US$8,010), and in the meantime ad spend went out prepaid every month, steadily draining cash.
- Splitting results by channel, search ads brought in 20 customers at a CAC of KRW 6.2 (≈ US$1) million, while industry trade shows brought in 8 at a CAC of KRW 24 million (≈ US$18,000). Trade-show customers also had a lower average contract value, so the following year the KRW 60 million (≈ US$44,900) booth budget was cut in half.
- The head of sales said, “A 5-point gain in renewal rate is worth two months of ad spend,” and assigned one customer success manager. The only rule they set was to report course progress to the client contact once a month during the first 90 days after onboarding.
- Nine months later, the renewal rate had risen from 78% to 86%, LTV had grown to KRW 53.1 (≈ US$1) million, and CAC had fallen to KRW 7.8 (≈ US$1) million, giving an LTV/CAC of 6.8x and a payback period of 12.6 months. Operating margin recovered from 4% to 9%.