What is paid CAC?
Paid CAC (Customer Acquisition Cost from paid channels) measures the cost to acquire a customer specifically through paid marketing — Google Ads, Meta, LinkedIn, paid search, paid social, and similar. It excludes organic channels (SEO, referrals, content), which are captured separately as Organic CAC.
The formula
Paid CAC = Total Paid Marketing Spend ÷ Customers Acquired via Paid Channels. The denominator requires accurate channel attribution — first-touch, last-touch, or multi-touch — which is the hardest part. A USD 100K monthly paid spend yielding 200 paid-attributed customers gives a USD 500 paid CAC.
Paid vs. blended vs. organic
Blended CAC divides total marketing spend by total customers — including organic — masking channel efficiency. Paid CAC isolates marketing-spend efficiency. Organic CAC includes content production, SEO investment, and partnership costs but excludes ad spend. VCs increasingly require all three be tracked separately because each scales differently.
Why paid CAC matters for SaaS scaling
Paid CAC scales linearly with budget — more spend, more customers — but at diminishing returns: channel saturation and rising auction prices increase paid CAC as scale grows. A startup with paid CAC of USD 500 at USD 100K monthly spend might face USD 800 paid CAC at USD 500K monthly spend. The LTV:CAC ratio test (target 3:1+) typically uses paid CAC because it’s the variable cost component.
VC due diligence implication
Top-quartile B2B SaaS companies maintain paid CAC payback periods under 12 months. If your business shows USD 1,000 paid CAC against USD 80 monthly ARPU, payback is 12.5 months — borderline. Founders should be ready to articulate paid CAC trajectory, channel mix, and scaling assumptions in any VC pitch.
Related: Organic CAC, Blended CAC, Contribution Margin, Hockey Stick Growth.