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What is LTV:CAC Ratio?

Definition of LTV:CAC ratio

LTV:CAC ratio compares the lifetime value of a customer (LTV) to the cost of acquiring them (CAC). It measures whether you generate more value from customers than you spend to win them.

LTV:CAC = Customer Lifetime Value / Customer Acquisition Cost

If your LTV is £600 and your CAC is £200, your LTV:CAC ratio is 3:1. For every £1 you spend acquiring a customer, you get £3 back over their lifetime.

It’s one of the most widely cited metrics in SaaS and B2B marketing, sitting alongside customer acquisition cost (CAC) and churn rate as a core unit economics metric.

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An example of LTV:CAC ratio

Growth Method spends an average of £150 to acquire a new customer. The average customer stays for 24 months and pays £50 per month, giving a lifetime value of £1,200. The LTV:CAC ratio is £1,200 / £150 = 8:1.

That sounds excellent — but it also raises a question. An 8:1 ratio might mean the company is under-investing in growth. More on that below.

How does LTV:CAC ratio work?

LTV:CAC works by combining two metrics that measure different timeframes. CAC captures a point-in-time acquisition cost. LTV estimates the total revenue (or profit) a customer generates over their entire relationship with your business.

The conventional benchmarks are:

LTV:CAC RatioWhat it usually means
Below 1:1You’re losing money on every customer
1:1 to 3:1Growth is inefficient or unsustainable
3:1The widely cited “healthy” benchmark
3:1 to 5:1Strong unit economics
Above 5:1Potentially under-investing in growth

The 3:1 benchmark has become industry shorthand, but as you’ll see from the expert opinions below, many practitioners question whether this number is meaningful — or whether LTV:CAC itself is the right metric to optimise.

To calculate LTV:CAC, you first need to understand how customer acquisition cost and churn rate work, since both feed directly into the formula.

Expert opinions and perspectives

LTV:CAC is one of the most debated metrics in SaaS and growth. Here’s what leading practitioners think.

The case for LTV:CAC (with caveats)

Emily Kramer, co-founder of MKT1, treats LTV:CAC as a practical efficiency metric. In her guide to marketing budgets, she writes that LTV:CAC ratio “indicates if growth is sustainable in the long-term” and notes that “if LTV:CAC is way over 3, you might be spending too conservatively to meet targets.” She recommends using it alongside CAC ratio and payback period rather than in isolation.

David Sacks, co-founder of Craft Ventures, accepts the 3x benchmark but adds nuance. He recommends checking that “healthy cohorts cross the $0 LTV line before month 12, and LTV grows to at least 3x original CAC over time.” He also introduced the burn multiple (net burn / net new ARR) as a complementary efficiency metric.

The case against LTV:CAC

Bill Gurley, partner at Benchmark, wrote the seminal critique back in 2012. His argument: LTV is dangerously seductive. “The LTV formula is a measurement tool to be used by marketing to test the effectiveness of their marketing spend — nothing more and nothing less,” he wrote. His warning was blunt — “you can’t win a fight with a measuring tape.” LTV doesn’t create competitive advantage; it just measures what’s already there.

Kyle Poyar, partner at Tremont and author of Growth Unhinged, argues CAC payback period is superior because “LTV is limitless for high-retention SaaS businesses.” When retention is strong, LTV approaches infinity — and an infinite ratio tells you nothing. His recommendation: “Forget LTV:CAC, look at [the Efficient Growth matrix] instead.”

Elena Verna, former interim head of growth at Dropbox, launched a “#death2cac” campaign arguing that optimising CAC in isolation is a trap. Her position: “The real hero is the velocity of the payback period” — how quickly you recoup acquisition cost matters more than the eventual lifetime ratio. As she puts it, “cheap acquisition is cheap for a reason.”

Brian Balfour, founder of Reforge, frames the problem differently. Rather than critiquing the ratio directly, he argues that CAC is structurally determined by your business model, not something you optimise with better ads. His insight: “You layer on new functionality/use cases that increase the LTV of customers and therefore increases the floor of what you can spend on CAC.” The ratio is an output of strategic decisions, not an input.

The AI-era critique

Jay Po at Stage 2 Capital argues LTV:CAC breaks down for modern companies: “It compresses time-based longitudinal data into a static ratio and assumes CAC, churn, contract value, and gross margin are all constant.” For AI-native and usage-based businesses, where all of these variables shift constantly, he recommends CAC Yield as a replacement — a metric that measures how your sales and marketing investments perform over time regardless of pricing model.

Kyle Poyar’s Rethinking SaaS Metrics for AI makes a similar argument — that the traditional SaaS metrics playbook can mislead when applied to consumption-based or AI-native companies where usage patterns and unit economics behave non-linearly.

Questions to ask yourself

Additional reading

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