LTV:CAC Ratio: The Most Important Marketing Metric
LTV:CAC is the master ratio that tells marketers whether acquisition spend is destroying value, breaking even, or ready to scale. Interviewers test metrics understanding at three levels: Do you know the formula? Can you interpret the number in context? Can you decide what to do based on it?
- LTV (Lifetime Value): The total net revenue a customer generates over their entire relationship with your brand.
- CAC (Customer Acquisition Cost): The total cost to acquire one new customer - all marketing + sales spend รท new customers.
- Simple LTV = Average Order Value ร Purchase Frequency ร Customer Lifespan.
- CAC = Total Marketing & Sales Spend / Number of New Customers Acquired.
- < 1:1 means losing money on every customer and is unsustainable.
- 3:1 is healthy and sustainable. The gold standard benchmark.
- 5:1+ is either very efficient OR under-investing in growth.
Big Picture: What LTV:CAC Tells You
LTV:CAC compares the total net revenue a customer generates over their entire relationship with your brand against the cost to acquire one new customer. The ratio is useful because CAC should always be judged relative to LTV: if LTV is โน10,000 and CAC is โน1,000, it is healthy; if CAC is โน8,000, it is unsustainable.
LTV (Lifetime Value): The total net revenue a customer generates over their entire relationship with your brand. CAC (Customer Acquisition Cost): The total cost to acquire one new customer (all marketing + sales spend รท new customers).
LTV:CAC Ratio - Visual Guide
LTV Calculation
Simple LTV = Average Order Value ร Purchase Frequency ร Customer Lifespan.
Example: โน800 AOV ร 4 orders/year ร 3 years = โน9,600 LTV.
Discounted LTV (more accurate) = ฮฃ (Monthly Revenue ร Gross Margin) / (1 + Discount Rate)n.
Quick SaaS LTV = ARPU / Monthly Churn Rate.
Example: โน500 ARPU / 5% monthly churn = โน10,000 LTV.
CAC Calculation
CAC = Total Marketing & Sales Spend / Number of New Customers Acquired.
- Blended CAC: All spend รท all new customers (includes organic)
- Paid CAC: Only paid marketing spend รท customers from paid channels
Example: โน10L marketing spend in January; 200 new customers - CAC = โน5,000.
CAC Payback Period
CAC Payback Period = CAC / (Monthly Revenue per Customer ร Gross Margin). Example: CAC = โน5,000; Monthly ARPU = โน500; Gross Margin = 70% - Payback = โน5,000 / (โน500 ร 0.7) = 14.3 months.
Worked Examples
For LTV, โน800 AOV ร 4 orders/year ร 3 years = โน9,600 LTV. For SaaS, โน500 ARPU / 5% monthly churn = โน10,000 LTV.
For CAC, โน10L marketing spend in January and 200 new customers gives CAC = โน5,000. For payback, CAC = โน5,000, Monthly ARPU = โน500, and Gross Margin = 70%, so Payback = โน5,000 / (โน500 ร 0.7) = 14.3 months.
Structuring a LTV Interview Answer
"What is customer lifetime value and why does it matter?"
Always specify blended vs paid CAC. Blended CAC is all spend รท all new customers and includes organic; paid CAC is only paid marketing spend รท customers from paid channels.
The common mistake is judging CAC without comparing it to LTV. Another mistake is treating 5:1+ as automatically best, when it can mean either very efficient OR under-investing in growth.
Conclusion
LTV:CAC is the core marketing metric for deciding whether growth is sustainable. Know the definitions, formulas, benchmarks, and CAC payback period, then connect the number to the right action.