Most teams cite LTV:CACas the north star of unit economics. It is measured quarterly, plastered on board decks, and used to defend every acquisition decision. And most of the time, it is wrong, or at least wrong enough to drive bad decisions.
The core problem
LTV is a projection. CACis historical. Mixing them into one ratio creates the illusion of precision where there is none. Worse, both numbers are typically calculated with fully-loaded costs on one side and fully-loaded revenue on the other, but in ways that are rarely consistent across finance, marketing, and ops teams.
In our CRO& Analytics engagements, the first week is often spent reconciling three different LTV definitions across a client's org. By the time we have one definition, the original LTV:CAC ratiosomeone was citing has shifted by 30–50%.
What we use instead
Payback period. Contribution margin by cohort. MER (marketing efficiency ratio). None of these are perfect in isolation, but together they triangulate reality better than a single ratio ever will.
The specific metrics depend on your business model. Consumable DTCbrands should obsess over repeat purchase rate and replenishment timing. Durable-good brands should track contribution margin by cohort over 24+ months. Subscription brands need churn-adjusted LTV on actual cohort data, not projections.
What to do this week
- →Pull your last 12 months of CACby cohort, not blended.
- →Calculate payback periodon contribution margin, not revenue.
- →Stop benchmarking against "industry standard" ratios, your business is the benchmark.
- →Track MER weekly alongside channel ROASto catch cannibalization early.
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Start Free AuditThe ratio isn't useless. It's just the wrong summary stat. Use it as a conversation starter, not a conclusion.
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