Overview
Customer Acquisition Cost (CAC) is the total cost of acquiring a new customer, including marketing, sales, and overhead expenses. For SaaS and subscription businesses, CAC is a critical metric paired with Lifetime Value (LTV) to determine sustainable growth. The golden rule: LTV should be 3x CAC or higher.
How to Calculate CAC
Formula: (Total Sales & Marketing Spend) / (Number of New Customers Acquired)
Example: Spent $100,000 on marketing/sales in a month, acquired 200 customers → CAC = $500.
Blended vs. Paid CAC:
- Blended CAC: Includes organic/referral customers (lower, but less actionable).
- Paid CAC: Only paid channel customers (higher, but shows channel efficiency).
Why CAC Matters
Unit Economics: If CAC > LTV, you lose money on every customer. If CAC payback period > 12 months, cash flow suffers. Channel Efficiency: Compare CAC across channels (Google Ads vs. content marketing vs. referrals) to allocate budget. Scalability: Can you profitably acquire more customers? If CAC increases as you scale, growth isn’t sustainable.
LTV:CAC Ratio
3:1 or higher: Healthy SaaS business (LTV 3x CAC). 1:1 or lower: Unsustainable — losing money on customers. 5:1+: Underinvesting in growth — could acquire more customers profitably.
Cultural Impact
CAC became the startup equivalent of unit economics. Investors scrutinized CAC trends: rising CAC signaled market saturation or poor product-market fit. Falling CAC indicated winner-takes-all dynamics or viral growth.
The metric drove strategy: CAC too high → improve conversion rates, reduce ad spend, focus on retention. LTV too low → increase pricing, reduce churn, upsell existing customers.
Criticism
CAC calculations varied wildly (some excluded salaries, others included overhead), making comparisons misleading. Startups gamed CAC by excluding expenses or using short time windows. The metric also ignored brand-building (long-term CAC reduction not measured).
Sources
- David Skok: SaaS Metrics 2.0
- ChartMogul: CAC Guide
- SaaStr: CAC Benchmarks