What is organic CAC?
Organic CAC (Organic Customer Acquisition Cost) measures the cost to acquire a customer through unpaid channels — SEO, content marketing, referrals, word-of-mouth, brand-led discovery. Counter-intuitively, organic CAC is rarely zero — it captures the cost of content production, SEO tools, design, community management, and PR that drive organic acquisition.
The formula
Organic CAC = (Content Production + SEO Investment + Brand/PR Spend + Partnership Costs + Allocated Salary for Organic Marketing) ÷ Customers Acquired via Organic Channels. The denominator requires accurate channel attribution. The numerator is harder than paid spend because it includes opportunity cost of time investment.
Why organic CAC is “sticky”
Unlike paid CAC, which scales linearly with budget, organic CAC has a long-lag investment profile: a blog post written today may produce customers 6-18 months later as it ranks in search. This creates accounting complexity — should you allocate this month’s content investment against this month’s organic customers? Most rigorous SaaS companies use 12-month rolling allocation.
The compound advantage
Organic channels compound: SEO authority grows with backlinks; content library accumulates value; word-of-mouth amplifies with NPS. After 24-36 months of investment, organic CAC for established SaaS often drops to USD 100-300 — meaningfully below paid CAC. Top-quartile B2B SaaS companies derive 40-60% of customers from organic channels by Series B.
VC due diligence focus
VCs increasingly probe the paid/organic split because it predicts CAC trajectory under scale. A company at 80% paid and 20% organic faces rising blended CAC as paid channels saturate; a company at 50/50 has more defensible economics. Founders should track and report both metrics separately from the earliest go-to-market motion.
Related: Paid CAC, Blended CAC, Contribution Margin, Hockey Stick Growth.