Growth alone doesn't prove a business model works, a company can acquire customers rapidly while spending more to get each one than that customer will ever generate in return, a pattern that only becomes visible when CAC and LTV are compared directly rather than tracked separately.
Calculating CAC correctly
CAC = total sales and marketing spend over a period ÷ number of new customers acquired in that same period. The common mistake is only counting ad spend and leaving out sales salaries, commissions, tools, and content costs that also contributed to acquiring those customers, which understates CAC and makes the business look healthier than it is. The CAC & LTV Calculator walks through both sides of this so the two numbers are calculated on a consistent, comparable basis.
Calculating LTV and why churn drives it
A simple LTV formula is average revenue per customer per period × average customer lifespan (in the same period units), and customer lifespan is directly tied to churn rate: lifespan ≈ 1 ÷ churn rate. A customer with a 5% monthly churn rate has an average lifespan of about 20 months, while a customer with 2% monthly churn averages 50 months, more than double the lifetime revenue from the same monthly spend, purely from a lower churn rate. This is why reducing churn is often a faster path to a healthier LTV:CAC ratio than trying to increase average revenue per customer.
Reading the ratio
A 1:1 ratio means you're spending exactly what each customer is worth, a losing position once you account for overhead beyond acquisition costs. A 3:1 ratio is the commonly cited healthy benchmark, high enough to fund operations and profit after acquisition costs. A ratio far above 5:1 isn't automatically better, it can actually signal underinvestment in growth, since spending more on acquisition (even at a lower ratio) might still be profitable and could grow the business faster. The Payback Period Calculator is a useful companion here, since it answers a related but distinct question: not whether a customer is worth acquiring, but how many months it takes to recover that acquisition cost.