Glossary - Acquisition and attribution
Blended CAC
Blended CAC (customer acquisition cost) is total sales and marketing spend divided by all new customers acquired in the period, whatever channel they arrived through. Ecommerce operators use it to track the true average cost of winning a customer, with no attribution model required, and judge it against margin per customer.
| Total S&M spend | Every marketing dollar in the period: paid media across all platforms, agency fees, affiliate commissions and other variable marketing costs. |
| New customers | First-time customers acquired in the period, whatever channel they came through - paid, organic, email or referral. |
Worked example
The first order recovers $45 of the $75 cost; the remaining $30 has to come from the contribution margin of repeat orders. How quickly that happens is the CAC payback question.
What is a good blended CAC?
There is no good blended CAC in isolation - $75 is cheap for one brand and ruinous for another. It only means something against what a customer returns in contribution margin: whether the first order covers it, what margin LTV accumulates over time, the LTV:CAC ratio, and how long payback takes.
Those in turn depend on your average order value, margin structure and repeat purchase behaviour, which is why cross-brand CAC comparisons mislead. Compute your own blended CAC, with NCAC beside it, in the free blended CAC calculator.
Blended CAC vs related metrics
| Metric | What it measures | How it differs from blended CAC |
|---|---|---|
| New-customer CAC (NCAC) | Acquisition-focused spend ÷ new customers. | Narrows the numerator to spend aimed at winning new customers, excluding retention marketing. |
| Marginal CAC | Δ spend ÷ Δ new customers between spend levels. | Prices the next cohort, not the average of the last - the CAC that governs the scale decision. |
| CAC payback | CAC ÷ monthly contribution margin per customer. | Turns the cost into a time: how many months until the customer has paid for themselves. |
| MER | Total revenue ÷ total marketing spend. | The same attribution-free logic pointed at revenue instead of customers. |
Common mistakes
- Dividing by all customers instead of new customers only. Returning buyers in the denominator make acquisition look cheaper than it is.
- Counting only ad spend. Agency fees, affiliate commissions and other variable marketing costs belong in the numerator.
- Reading the blended average as the price of the next customer. Marginal CAC is usually higher, and it is the one that governs whether to scale.
- Judging CAC with no margin next to it. A high CAC can be healthy with strong repeat margin, and a low CAC fatal on thin margin.
- Using blended CAC to evaluate one channel. It cannot allocate credit; per-channel CAC is where an attribution model becomes necessary.
FAQ
No - that is its advantage. Total spend divided by total new customers needs no attribution model, which is why it stays trustworthy when platform-reported numbers disagree with each other.
Because new customers arriving through organic, email and referral enter the denominator without adding ad cost, while a platform CAC counts only its own spend against its own attributed conversions.
Everything variable that you spend to win customers: paid media across platforms, agency fees, affiliate commissions and promo costs. Leaving any of it out understates CAC.
Related
- New-customer CAC (NCAC)
- Marginal CAC
- CAC payback
- LTV:CAC ratio
- MER (marketing efficiency ratio)
- Blended CAC calculator
- All 14 free tools →
In Blufire, S2 Unit Economics tracks CAC, NCAC, CM-payback, LTV:CAC and Marginal CAC & Saturation, computed on reconciled margin rather than platform-reported revenue.
Updated July 2026