CAC (Customer Acquisition Cost)
Also known as: Customer Acquisition Cost, acquisition cost
The total marketing cost to acquire one new customer.
CAC is the honest cost of a new customer. Where ROAS flatters retargeting and CPA mixes new + repeat, CAC forces the question the CFO cares about: how much are we paying per net-new buyer, and how quickly do they pay back?
Definition
CAC is total sales-and-marketing spend divided by newly acquired customers in the same period. It differs from CPA in that CAC counts only new customers, not any conversion event.
Why it matters
CAC vs LTV determines whether growth is compounding value or burning cash. Every strategic decision — bid, channel mix, offer — eventually resolves to 'does this move CAC in the right direction?'.
Formula
CAC = Total S&M Spend ÷ New Customers
| Definition | Includes org. | Numerator | Denominator | |
|---|---|---|---|---|
| CAC (blended) | Total S&M ÷ new customers | Yes | All S&M costs | New customers |
| CAC (paid) | Paid spend ÷ paid customers | No | Paid media only | Paid new customers |
| CPA | Spend ÷ conversions | No | Ad spend | Any conversion event |
CAC vs CPA — the same data can produce very different numbers.
Blended CAC vs paid CAC
Blended CAC divides total S&M spend by all new customers — including organic and word-of-mouth. Paid CAC restricts to paid customers acquired through paid channels. Track both. Blended CAC tells you if the whole growth engine is efficient; paid CAC tells you if the ad account is.
Why CAC rises with scale
Auction pressure grows as you widen audiences beyond the highest-intent core. Every incremental dollar of spend reaches slightly colder users, slightly worse custom audiences, and slightly higher CPMs. A rising CAC isn't automatically bad — it's expected. Judge it against updated LTV, not against yesterday's floor.
$60,000 blended marketing spend brought 800 new customers → CAC = $75.
Common mistakes
- ✕Confusing CAC with CPA — CPA counts every conversion, CAC counts only new customers.
- ✕Excluding creator, tools, or agency costs from the numerator.
- ✕Not separating blended CAC from paid CAC.
- ✕Comparing CAC across channels without normalising for cohort quality.