What the Calculator Calculates
Customer Acquisition Cost (CAC) is your total sales and marketing spend divided by the new customers acquired in the same period. Lifetime Value (LTV) is the gross margin a customer generates over the time they stay, most simply estimated as average revenue per user divided by the churn rate. The LTV/CAC ratio compares the two: it tells you whether the money you spend to win a customer comes back more than once.
Unit economics are the layer of the income statement that survives every growth narrative. A startup can show explosive top-line growth and still be destroying value if every new dollar of revenue costs more to acquire than it returns. Investors check LTV/CAC before they check growth rate, because it reveals whether the machine is efficient or subsidized.
How to Interpret the Results
A ratio of 3x means each customer returns three times what it cost to acquire — the minimum most investors accept. Above 5x is excellent, though an extremely high ratio can also signal that you are under-investing in growth. The companion metric is payback period: CAC divided by monthly gross margin per customer tells you how many months it takes to earn back the acquisition spend. Payback under 12 months is the working standard for venture-backed SaaS.
Use Cases
- Fundraising preparation: have your CAC, LTV, and payback numbers ready before the first investor call — vague unit economics is a top diligence turnoff.
- Channel decisions: compute LTV/CAC per channel (paid ads, content, partnerships) and shift budget to the channels that clear the 3x bar.
- Portfolio monitoring: for existing investments, a deteriorating LTV/CAC is an early warning that growth is becoming expensive.
- Business model sanity checks: if CAC is higher than first-year revenue and churn is high, the model needs fixing before it scales.
The Engineering Connection
LTV is ultimately a product metric: retention, expansion, and gross margin all depend on how well the team ships. GitDealFlow's engineering velocity data gives an outside-in view of that engine — commit velocity, contributor growth, and repository expansion across 4,200+ startups. Teams that keep shipping at high velocity tend to compound product quality, which drives the retention that makes LTV real.
Frequently Asked Questions
What's a healthy LTV/CAC ratio?
3x minimum, 5x+ excellent. Below 3x means you're spending too much to acquire customers.
What is CAC payback period?
CAC divided by monthly gross margin per customer — the months needed to earn back acquisition spend. Under 12 months is the standard for venture-backed SaaS.
Why does LTV depend on churn?
LTV is roughly ARPU divided by churn rate — lower churn extends customer lifetime and multiplies value, which is why retention is the highest-leverage metric in SaaS.