What is LTV:CAC ratio?

A business whose customers contribute A$324 over the relationship and cost A$108 to acquire has a ratio of 324 ÷ 108 = 3.0. Raise acquisition cost to A$162 while chasing growth and the ratio falls to 2.0 — still economic, with less room for everything the contribution also has to pay for. Push spend until acquisition cost reaches A$324 and the ratio is 1.0, at which point every customer won pays for their own advertising and contributes nothing to rent, salaries or profit.

The ratio divides what a customer is worth over the relationship by what it cost to win them. It compresses the two most important numbers in a subscription or repeat-purchase business into one, and it answers a single question: is acquiring customers economic at all.

The appeal is that it is independent of scale. A business acquiring customers at A$40 who are worth A$120 and a business acquiring them at A$4,000 who are worth A$12,000 have the same answer to that question, and can be discussed in the same terms. That property is why the ratio ended up on every board pack.

The corresponding weakness is that scale-free numbers throw away the information that constrains real decisions, and in this case the discarded information is cash.

The commonly quoted target of three to one originated in software businesses with high gross margins and recurring revenue, and the reasoning behind it is worth knowing because it determines when the target transfers.

The argument is that the contribution a customer produces has to cover three things: the cost of acquiring them, the cost of serving and supporting them, and a surplus for fixed costs and profit. If acquisition takes a third, roughly two thirds remain for everything else, which was about right for the businesses the rule was derived from.

That logic does not transfer automatically. A business with a 30% gross margin has far less room than one with 80%, and needs a higher ratio to fund the same overhead. A business deliberately buying market share with investor capital can run below the target on purpose for a defined period. A mature business with low fixed costs can operate below it indefinitely.

The rule's real value is as a prompt to derive your own target from your own cost structure. Take the contribution, subtract what the rest of the business needs, and the remainder is what acquisition can have. That is the number to manage against.

The ratio inherits every weakness of its two inputs, and multiplies them.

On the value side, the common failure is stating it as revenue rather than contribution. That alone can double the figure. The second is an unreasonable horizon: a five-year projection built from a year of data puts most of the number in years nobody has observed.

On the cost side, the common failure is using media spend alone — the figure the ad platform reports — rather than the full cost of acquisition including agency fees, creative production, tooling and sales salaries. In a business with a sales team that understates the denominator by a factor of two.

Make both mistakes at once, which is easy and common, and a genuine two-to-one business reports eight to one. Every decision made downstream of that number will be wrong in the same direction, and the error will only surface in the bank balance.

The discipline is unglamorous: state what is in each half, in writing, and compute both over matching periods.

This is the failure mode the metric is least able to warn about.

Consider a business whose customers contribute A$900 over three years and cost A$400 to acquire. The ratio is better than two to one. It is also a business that pays A$400 today and waits, on average, well over a year to get it back. Double the acquisition rate and the cash requirement doubles immediately while the returning contribution does not.

This is why payback period sits beside the ratio in any serious review, and why a company with excellent unit economics can still run out of money. Growth funded from operating cash is limited by how fast contribution comes back, not by how much of it eventually arrives.

The practical consequence for advertising is that a long payback narrows the range of acquisition tactics the business can afford, regardless of how good the lifetime arithmetic looks. Channels that produce customers who pay quickly are worth more than the ratio alone suggests.

The most consistently misread case is a ratio well above target.

Six to one is rarely evidence of unusual skill. In almost every case it means the account is buying only the cheapest customers — branded search, retargeting, the warmest audiences — and declining to compete for everything else. The customers being left behind are worth something, and a competitor is buying them.

Because the marginal customer always costs more than the average one, spending more lowers the ratio by construction. That is the correct direction of travel when the ratio sits above target: increase spend until it approaches the number the cost structure actually requires, and take the volume.

The instinct to protect a high ratio is strong and expensive. It optimises a number rather than the business.

A blended company-wide ratio can conceal almost anything. One channel at six to one and another at one to one average out to a respectable figure, and the average gives no instruction about either.

Useful cuts: by acquisition channel, by cohort month, by first product purchased, and by whether the first purchase was discounted. Each of those segments frequently has a different lifetime value and a different acquisition cost, which means each has its own ceiling and can be bid to it.

The blended figure keeps its place as the control. Attribution systems credit the same customer to several channels, so per-channel ratios are collectively optimistic; if every channel reports a healthy ratio while the blended figure deteriorates, the attribution is the thing that needs attention rather than the campaigns.

Both halves move, and the value half is usually the more neglected.

On the cost side: creative, exclusions, landing pages, close rate, and the mix of channels. On the value side: order value, purchase frequency, retention, and gross margin. A single point of gross margin applies to every customer the business will ever acquire, which makes it one of the highest-leverage numbers in the whole calculation and one almost never discussed in an advertising review.

And the third lever is which customers arrive. Acquisition decides the mix, and a channel that brings in customers who come back raises the ratio on both sides at once.

• Check that both halves are computed in contribution and over matching periods before reading the ratio at all. A revenue-based lifetime value against a media-only acquisition cost can overstate the ratio by a factor of four.
• Read it beside payback period, never instead of it. A strong ratio with a long payback is the shape of a business that grows itself into a cash problem.
• Compute it by cohort and by channel. A blended ratio of three to one can hide one channel at six and another at one, and the blended figure gives no instruction about either.
• Treat a very high ratio as a signal to spend more. Five or six to one usually means the account is under-invested and conceding volume, not that it is unusually well run.
• Recompute it when the mix changes, not on a schedule. New channels, new offers and new discount levels all move both halves, and a quarterly cadence will report the change after the decisions that depended on it.