What is the difference between CPA and CAC?

CPA usually counts ad spend per conversion; CAC counts fully-loaded sales and marketing cost per new customer.

Is a low CPA always good?

No — a low CPA on low-quality conversions that never become customers can be worse than a higher CPA on quality ones.

Growth Marketing Glossary

CPA

noun (initialism)

What one conversion costs in advertising — the channel-level cousin of customer acquisition cost.

Schematic — cost per conversion

Term: CPA
Stands for: Cost Per Acquisition / Action
Part of speech: Noun
Field: Paid Media

Forms & parts of speech

CPA · noun (initialism)

Ad cost divided by conversions.

"Our paid-search CPA is $35 per lead; on display it's closer to $90."

Definition in plain terms

CPA is the average advertising cost to produce one conversion — a lead, signup, or sale, depending on how you define the action. It measures channel-level acquisition efficiency, and unlike CAC it usually counts only ad spend rather than fully-loaded sales-and-marketing cost.

The mechanics

Divide the advertising cost by the number of conversions over the same period. "Acquisition" and "action" are used interchangeably; what counts as a conversion is a definition you set, so two CPAs are only comparable if they measure the same action.

When it matters

CPA is the working metric for optimizing paid channels day to day, but it is only meaningful next to the value of the conversion. A low CPA on low-quality leads that never become customers is worse than a higher CPA on leads that convert — which is why CPA should be read alongside downstream value, not in isolation.

Worked example. A campaign spends $3,500 and produces 100 conversions. CPA = $3,500 ÷ 100 = $35 per conversion. If those conversions are leads that close at 10% into $500 customers, the effective cost per customer is $350 — a different and more decision-relevant number than the headline $35 CPA.

Failure modes to watch. Optimizing CPA without checking lead quality (cheap conversions that never become customers); comparing CPAs that measure different actions; and confusing channel CPA with fully-loaded CAC.

Formula

CPA = Advertising cost ÷ ConversionsDefine the conversion explicitly. CPA usually counts ad spend only; CAC counts fully-loaded sales & marketing cost.

Benchmarks

CPA has no universal benchmark — it only means something relative to what each conversion is worth.

No universal benchmark

Depends on the action & its value

Read against

The value of the conversion

Channel variance

Search vs. display vs. social differ widely

Calculator

CPA calculator →

Ranges are illustrative; every published figure is cited from a named public source or labelled “RGM analysis.”

Synonyms & antonyms

Synonyms

cost per acquisitioncost per actioncost per conversion

Usage trends

Search interest for this term over the last five years:

View interest-over-time on Google Trends →

Common questions

What is the difference between CPA and CAC?: CPA usually counts ad spend per conversion; CAC counts fully-loaded sales and marketing cost per new customer.
How do you calculate CPA?: Divide advertising cost by the number of conversions over the same period.
Is a low CPA always good?: No — a low CPA on low-quality conversions that never become customers can be worse than a higher CPA on quality ones.