Customer Acquisition Cost (CAC) and Customer Lifetime Value (LTV) are the two most important metrics in subscription business economics. CAC measures how much you spend to acquire a customer; LTV measures how much revenue that customer generates over their entire relationship with your business. The ratio between them determines whether your business can scale profitably or is burning cash unsustainably.
The Formulas
CAC = Total Sales & Marketing Spend / New Customers Acquired LTV = Average Revenue per Customer × Average Customer Lifespan LTV = ARPU / Monthly Churn Rate The LTV:CAC Ratio
| LTV:CAC Ratio | What It Means | Action |
|---|---|---|
| Below 1:1 | Losing money on every customer | Fix product-market fit, pricing, or churn immediately |
| 1:1 to 3:1 | Marginally profitable or unprofitable | Reduce CAC or increase retention/upsells |
| 3:1 | Healthy unit economics (benchmark) | Scale acquisition spending |
| 5:1+ | Very efficient but possibly under-investing | Increase marketing spend to accelerate growth |
A ratio of 3:1 or higher is the widely accepted benchmark for healthy SaaS unit economics. This means every $1 spent on acquisition generates $3 in lifetime revenue. Below 3:1, you are likely spending too much to acquire customers relative to their value. Above 5:1, you may be leaving growth on the table by not investing enough in acquisition.
CAC Payback Period
The LTV:CAC ratio tells you whether the math works long-term, but the CAC payback period tells you how long it takes. Payback Period = CAC / Monthly Gross Margin per Customer. If CAC is $600 and monthly gross margin per customer is $80, payback is 7.5 months. Good SaaS companies recover CAC in under 12 months; great ones in under 6.
How to Improve the Ratio
- Reduce CAC: Focus on organic channels (SEO, content, referrals) that have lower acquisition costs than paid advertising. Improve conversion rates on your website and sales process.
- Increase LTV: Reduce churn (the highest-leverage move), build upsell and cross-sell paths, and increase prices for new customers. Use the LTV Calculator to model these changes.
- Segment by channel: Calculate CAC and LTV separately for each acquisition channel. You may find that Google Ads has a 2:1 ratio while organic SEO has 8:1, suggesting reallocation of budget.
Key Takeaways
- LTV:CAC of 3:1 is the target ratio for healthy SaaS unit economics.
- CAC payback under 12 months indicates efficient customer acquisition.
- Reducing churn is the most powerful lever for improving LTV and the ratio.
- Segment by channel to identify which acquisition sources provide the best economics.
- A ratio above 5:1 may mean you are under-investing in growth.
Frequently Asked Questions
What is a good CAC for SaaS?
CAC varies enormously by market segment. B2C SaaS typically has CAC of $50-$200. B2B SMB SaaS averages $200-$1,000. Enterprise SaaS can have CAC of $5,000-$50,000+. The absolute number matters less than the LTV:CAC ratio; a $10,000 CAC is fine if LTV is $30,000+.
Should I include salaries in CAC?
Yes, fully loaded CAC includes all sales and marketing costs: ad spend, salaries and commissions for sales and marketing teams, tools and software, events, and content creation. Some companies also calculate a blended CAC that includes customer success costs for onboarding. Excluding salaries gives a misleadingly low CAC.
How do I calculate LTV for a new business with no historical data?
Use cohort analysis of your earliest customers to estimate churn and expansion rates. If you have 6+ months of data, calculate monthly churn from the surviving cohort percentage and use LTV = ARPU / Churn Rate. For pre-revenue companies, use industry benchmarks and competitor analysis to estimate, then update as real data becomes available.