LTV:CAC ratio

Customer lifetime value (LTV) is the total margin a business expects to earn from a customer over the length of the relationship, and customer acquisition cost (CAC) is the average cost of winning a new customer, calculated from sales and marketing spend.

The LTV:CAC ratio compares the lifetime value of a customer to the cost of acquiring that customer, expressed as a ratio such as 3:1, to show whether a business generates enough long-term value from a customer relationship to justify what it spent to win it.

A higher ratio generally points to a more efficient go-to-market motion, while a low ratio suggests a business is spending too much to acquire customers relative to what those customers return over time.

For a subscription business, the LTV:CAC ratio is one of the clearest signals of unit economics health, since it combines two numbers that are each already central to planning: how much a customer is worth over the relationship, and how much it costs to bring that customer on board. A subscription platform such as Recurly provides the underlying revenue, retention, and churn data that feeds the LTV side of this calculation, while CAC is typically pulled from sales and marketing spend records outside the billing system.

Why the LTV:CAC ratio matters for subscription businesses

Because a subscription business earns revenue from a customer over many billing cycles rather than in a single transaction, the relationship between what a customer is worth and what it costs to acquire them is central to whether the growth strategy is sustainable. A business that grows revenue quickly by spending heavily on acquisition can still be destroying value if the resulting customers do not stay long enough or spend enough to recoup that cost.

Investors, boards, and internal finance and RevOps teams use the LTV:CAC ratio as a standard lens for evaluating whether a subscription business's growth is efficient, and it is commonly tracked alongside other unit economics metrics like CAC payback period and gross margin.

How to calculate the LTV:CAC ratio

The LTV:CAC ratio is calculated by dividing customer lifetime value by customer acquisition cost:

LTV:CAC ratio = Customer lifetime value (LTV) / Customer acquisition cost (CAC)

Each input is itself typically derived from other metrics:

LTV = Average revenue per customer per period x Gross margin percentage x Average customer lifespan (or 1 / churn rate)

CAC = Total sales and marketing spend over a period / Number of new customers acquired in that period

One caution on the LTV side: treating LTV as an infinite annuity by using 1 / churn rate usually overstates it, because it assumes a customer relationship that never ends. More rigorous models cap the assumed customer lifespan, commonly at around seven years, rather than projecting it indefinitely.

To calculate the ratio for a subscription business:

1. Calculate average revenue per customer for a defined period, such as monthly or annual recurring revenue divided by the number of customers.

2. Apply the business's gross margin percentage to that revenue figure to reflect the actual value delivered, not just top-line revenue.

3. Estimate average customer lifespan, commonly as the inverse of the churn rate for the same period (for example, a 2 percent monthly churn rate implies an average lifespan of 1 divided by 0.02, or 50 months).

4. Multiply average gross margin per customer by average lifespan to arrive at LTV.

5. Calculate CAC by dividing total sales and marketing spend for a period by the number of new customers acquired in that same period.

6. Divide LTV by CAC to get the ratio, typically expressed as LTV:CAC (for example, 3:1).

How to use the LTV:CAC ratio

The LTV:CAC ratio is most useful when tracked consistently over time and segmented rather than treated as a single headline number.

• Calculate it by acquisition channel or customer segment, since a blended company-wide ratio can hide channels that perform very differently from one another.

• Track it alongside CAC payback period, since a healthy ratio calculated over a very long assumed customer lifespan can mask a cash flow problem if payback takes too long.

• Recalculate it regularly as churn, pricing, and acquisition costs change, rather than treating it as a fixed, one-time benchmark.

• Use it to inform decisions about scaling or pulling back specific acquisition channels, since a channel with a strong ratio is generally a better candidate for additional investment than one with a weak ratio.

• Read a low ratio as a sign that acquisition spend is running ahead of the value customers return, and read an unusually high ratio as a possible sign of underinvestment in growth rather than a result to celebrate.

Reading the ratio

• Roughly 3:1 is the conventional healthy benchmark: you recover 3x what you spend to land a customer.

• Below 1:1, you're losing money on every customer.

• Above 5:1 usually signals under-investment in growth, not virtue; you could spend more and still be efficient.

Benefits and examples

Tracking the LTV:CAC ratio deliberately gives a subscription business several benefits:

• A single, comparable number that summarizes whether growth spend is translating into durable value, useful for board and investor conversations.

• A way to compare the efficiency of different acquisition channels or customer segments against each other on a like-for-like basis.

• An early warning signal, when the ratio trends down over time, that acquisition costs are rising faster than customer value, or that retention is weakening.

As an illustrative example, imagine a subscription business with an average customer paying 100 dollars per month, a gross margin of 80 percent, and a monthly churn rate of 2 percent. Average gross margin per customer per month is 80 dollars (100 dollars times 0.80). Average customer lifespan is 50 months (1 divided by 0.02). LTV is therefore 4,000 dollars (80 dollars times 50 months). If the business spends 500,000 dollars on sales and marketing in a period and acquires 500 new customers in that same period, CAC is 1,000 dollars (500,000 dollars divided by 500). The LTV:CAC ratio is 4,000 divided by 1,000, or 4:1.

Frequently asked questions

What is considered a good LTV:CAC ratio? Many subscription businesses aim for a ratio that comfortably clears the cost of acquisition, though the specific benchmark depends on the business model, growth stage, and industry. A ratio that is too low suggests inefficient acquisition spend, while an unusually high ratio can sometimes indicate underinvestment in growth.

What's the difference between LTV:CAC ratio and CAC payback period? The LTV:CAC ratio measures the total value a customer generates relative to what it cost to acquire them over their entire relationship with the business. CAC payback period measures how long it takes, typically in months, to recover the acquisition cost from that customer's margin contribution. A business can have a strong LTV:CAC ratio and still have a slow payback period if most of the value is realized late in a long customer lifespan.

Why does gross margin matter in the LTV calculation? Using gross margin rather than raw revenue in the LTV calculation reflects the actual value a customer contributes after the cost of delivering the product or service, which gives a more accurate picture of how much acquisition spend that customer can support.

How often should a subscription business recalculate its LTV:CAC ratio? Most finance and RevOps teams recalculate it on a regular reporting cadence, such as quarterly, and whenever there is a significant shift in churn, pricing, or acquisition spend, since all three inputs can move meaningfully over shorter time frames.