CPA (Cost per Acquisition / Action)

Metric

CPA is the average advertising cost required to generate one specific conversion event, such as a lead, trial signup, or purchase.

Layman Explanation & Analogy

CPA tells you the price tag of a specific user action. If you spent $500 on an ad campaign and got 25 webinar registrations, your CPA for a webinar lead was $20.

Mathematical Formula

CPA = Ad Spend ÷ Total Target Conversions

Worked real-world example

Spending $2,000 to generate 80 new customer signups yields a CPA of $2,000 ÷ 80 = $25 per signup.

What people get wrong & common traps

Comparing CPAs across different campaigns is invalid if the conversion events have different values — a $10 CPA for an email newsletter is completely different from a $50 CPA for a paying $500 software customer.

Related terms

Blended CAC
CPC
CTR