LTV:CAC Ratio
The ratio of customer lifetime value to customer acquisition cost — the fundamental unit-economics test of whether a business model works.
What Is the LTV:CAC Ratio?
LTV:CAC is the ratio of estimated customer lifetime value to customer acquisition cost. It compares modeled gross profit from a customer with the cost to acquire that customer. Its interpretation depends on the LTV method, margin, payback timing, uncertainty, and business model.
Also Known As
- Finance teams: unit economics ratio, LTV:CAC multiple
- Growth teams: payback efficiency
- Investor view: capital efficiency ratio
- Board reports: lifetime-value ratio
How It Works
Illustrative simplified example: A SaaS customer pays $100 per month with 80% gross margin and 3% constant monthly churn. Ignoring expansion, discounting, and churn variation, LTV = ($100 × 0.80) / 0.03 = $2,667. If blended CAC is $800, LTV:CAC is about 3.3; if CAC rises to $1,500, it falls to about 1.8. The change is a signal to inspect marginal acquisition economics, not a universal scale-or-stop threshold.
Best Practices
- Do use gross-margin-adjusted LTV, not raw revenue × lifetime. Revenue that doesn't contribute margin isn't real LTV.
- Do compute LTV and CAC by channel. Blended ratios can hide a channel that's bleeding money.
- Do use cohort-based LTV, not modeled LTV, when possible. Real data beats formulas.
- Don't optimize the ratio in isolation. A high ratio can reflect efficient acquisition, constrained growth, conservative spend, or an overstated LTV model.
- Don't inflate LTV with expansion you can't actually predict. Be conservative.
Common Mistakes
- Using revenue LTV instead of gross profit LTV. An 80% margin business and a 20% margin business with the same LTV:CAC are not comparable.
- Ignoring payback period. A healthy LTV:CAC with a 36-month payback still strains cash flow.
Industry Context
Useful LTV:CAC ranges differ by margin, cash timing, repeat behavior, sales cycle, and risk. Compare cohorts using a consistent calculation and use benchmarks only when their definitions and business model match yours.
The Behavioral Science Connection
LTV:CAC is the business equivalent of expected value calculation — it forces teams to reason about probability-weighted future value rather than relying on short-term optimism. It counters sunk cost fallacy in channel decisions: the fact that you've spent $2M on a channel doesn't matter if the current ratio is 0.8.
Key Takeaway
LTV:CAC is a useful unit-economics estimate, but it is only as credible as its inputs. Pair it with observed payback, retention, cash flow, and sensitivity analysis before making a spending decision.