Lifetime value is average order value times orders per year times customer lifespan, times gross margin. A 50 order four times a year for three years at a 50 per cent margin gives 300 of lifetime gross profit, which against a 100 acquisition cost is the 3:1 ratio people quote. Drop the margin step and the same customer looks like 600 — a 6:1 ratio, on identical performance.
That is the first question to ask about any published LTV: margin-based or revenue-based. Companies quoting the bigger number rarely say which they used.
What goes into each figure?
Three inputs to LTV and two to CAC, and the definitions are where the argument lives.
| Figure | Calculation | The judgement call |
|---|---|---|
| AOV | Revenue ÷ orders | Whether shipping and tax are in the revenue |
| LTV | AOV × frequency × lifespan × margin | Whether margin is applied at all |
| CAC | Sales and marketing cost ÷ new customers | Whether salaries are included |
| Ratio | LTV ÷ CAC | Both of the above |
A fully loaded CAC includes the people as well as the media: 9,000 of media plus 1,000 of salaries across 100 customers is 100, against a media-only figure of 90. Both are defensible and they are not the same number, so a ratio built from one and compared against a ratio built from the other says nothing.
What is the period mismatch?
The subtle error in almost every CAC calculation. Spend in January often wins customers in March, so dividing one month’s spend by the same month’s customers is noisy at best and simply wrong for anything with a long consideration cycle.
A rolling three-month window smooths it for most consumer businesses. For anything with a sales cycle measured in months, the honest version is a cohort: track the customers won from a specific spend period, however long they take to arrive.
Why is the 3:1 ratio treated as a rule?
Because it leaves room for everything LTV does not include. Gross profit is not net profit — rent, salaries, software and support all come out afterwards — so a business at 1:1 is losing money on every customer and a business at 3:1 has some headroom.
It is a heuristic rather than a target. A business with very low fixed costs can work at 2:1; one with a heavy support burden may need 5:1. Quoting the ratio without the cost structure behind it is repeating a number rather than measuring anything.
The payback period is often the more actionable figure: how many months of gross profit it takes to recover the acquisition cost. Twelve months or less is comfortable for most consumer businesses because it means growth funds itself within a year.
Where does break-even sit?
At the point where contribution covers the fixed costs. Break-even units are fixed costs divided by contribution per unit: 5,000 of fixed costs, a 25 price and a 10 variable cost gives 15 of contribution and 334 units, or 8,350 of revenue.
The more useful output is the contribution margin itself, because it tells you which lever moves the answer fastest. On a 60 per cent contribution margin, a 10 per cent price rise cuts the break-even volume by about a seventh; the same 10 per cent off variable costs does considerably less.
That asymmetry is why price is almost always the strongest lever and the one businesses are most reluctant to pull.
What makes LTV figures incomparable?
Three conventions, none of which is standard.
- Margin applied or not, which changes the answer by the margin itself.
- Discounting future value, since profit in year three is worth less than profit today, and most simple LTV models ignore this.
- Lifespan estimated or observed. A three-year lifespan assumed for a two-year-old business is a forecast wearing a measurement’s clothes.
The practical response is to publish your own definition alongside the number and to compare only against your own history. Benchmarks against other companies’ LTV figures are almost always comparing two different calculations.
Questions people ask
Should CAC include organic customers? If the denominator is all new customers, the ratio flatters the paid channels. Blended CAC across everything and paid CAC against paid customers answer different questions, and both are worth having.
What is a good AOV? Only comparable within a category. The useful comparison is against your own trend and against the threshold and bundling changes you made.
Does LTV include returns? It should. A 20 per cent return rate removes a fifth of the revenue and leaves the fulfilment cost behind, which is a substantially worse outcome than a fifth fewer orders.
How long a lifespan should I assume? For a business with real history, the observed one. Otherwise use a short assumption and revise it — an optimistic lifespan is the easiest way to make a bad unit economic look fine.
Is a ratio enough on its own? No. A 5:1 ratio on a twenty-four-month payback can be worse for a business than 3:1 on a six-month one, because the second funds its own growth and the first needs capital to bridge the gap.
Define the terms first, then the ratio means something. The LTV calculator applies margin explicitly, the CAC calculator separates media from fully loaded cost, the AOV calculator reports revenue per customer alongside per order, and the break-even calculator shows the contribution margin that decides which lever to pull.