LTV-To-CAC Thresholds By Business Model

Three to one is the number everyone repeats and it is close to useless on its own, because it says nothing about how long the payback takes or how confident you are in the lifetime figure.

Two businesses can both run at three to one and one of them is healthy while the other is running out of cash.

What the ratio actually assumes

Lifetime value divided by acquisition cost assumes you will collect that lifetime value. On a monthly service with real churn, a large share of it is a forecast rather than money.

The longer the payback period, the more of that ratio is a promise. That is the part the headline number hides.

Payback period is the number that constrains you

How many months of gross profit from a customer it takes to recover what you spent acquiring them.

Under three months, you can reinvest fast and growth is largely limited by demand. Around six to twelve months, growth is limited by cash and you need funding or patience. Beyond eighteen months, you are running a financing operation with a marketing department attached.

Two businesses at the same ratio with different payback periods are not comparable, and payback is the one that determines how fast you can grow without borrowing.

Use gross profit, not revenue

Lifetime value calculated on revenue overstates everything. The relevant figure is the margin left after delivering the service.

For a business with heavy delivery costs, the difference between the two versions is enormous, and it is the reason some businesses feel unprofitable at a ratio that looks fine on paper.

Where the thresholds actually differ

High margin, low churn, long contracts. Software and retained services. Longer payback is tolerable because the revenue is predictable and the margin is high, so a lower ratio can still be a good business.

High margin, high churn. The ratio needs to be higher, because the lifetime value estimate is fragile. A small increase in churn moves the whole calculation.

Low margin, transactional. The ratio has to be much higher because there is little margin to absorb error, and lifetime value is usually short.

Long sales cycles with large contract values. The ratio can be excellent and the cash position still difficult, because the payback sits a long way out.

The mistakes that make the number meaningless

Excluding the cost of your own team from acquisition cost. If people spend time selling, that time is acquisition cost.

Calculating lifetime value on your best cohort. Use the average, including the ones who left early.

Using an average across mixed segments. If one channel produces customers who stay three years and another produces customers who stay four months, the blended figure describes neither.

Ignoring the payback distribution. An average payback of eight months made up of half at two months and half at fourteen is a completely different business to one where everyone pays back at eight.

The version worth reporting

Gross-profit lifetime value to fully loaded acquisition cost, segmented by channel, with the payback period beside it.

Four numbers instead of one, and the four of them tell you what to do next. The single ratio tells you nothing except whether to feel good.