A single blended CAC number is easy to report and easy to misread. It averages your best and worst-performing channels into one figure that describes none of them accurately.
The formulas
Why blended CAC hides the real picture
Imagine $30,000 spent across two channels: $25,000 on paid ads generating 25 customers ($1,000 CAC) and $5,000 on SEO/content generating 20 customers ($250 CAC). Blended CAC reports $667 — a number that describes neither channel and obscures a 4× efficiency gap sitting right there in the data.
What channel-level CAC changes about your decisions
With the breakdown visible, the obvious move is to shift budget from paid ads toward content/SEO until the marginal CAC on each channel converges — a decision blended CAC alone would never surface. Teams that only track blended CAC routinely keep overfunding their least efficient channel simply because it's not visibly underperforming.
When blended CAC is still useful
Blended CAC remains the right number for comparing against LTV at the company level (LTV:CAC ratio) and for investor reporting, where a single top-line efficiency metric is expected. Use it for the headline number, and channel CAC for the operating decision of where to spend the next marketing dollar.
A word on attribution
Channel-level CAC is only as good as your attribution model. Last-touch attribution is the simplest starting point; multi-touch attribution gives a fuller picture for longer, multi-channel buying journeys but requires more sophisticated tracking to set up correctly.
Frequently asked questions
How many channels should I track separately? Start with your 3–5 largest spend channels. Smaller experimental channels can be grouped into an "other" bucket until they earn a dedicated line.
Should I include organic/referral traffic with $0 spend? Yes — it will show as near-zero CAC, which is useful context, but treat it as a bonus channel you can't easily scale rather than a primary acquisition strategy.
Use the CAC by Channel Calculator to compare CAC across your own marketing channels side by side.