CPA (Cost Per Acquisition / Action)
Cost Per Acquisition is the amount you pay to achieve one conversion — a sale, signup, or admit. It's the marketer's primary efficiency metric.
What it is
Cost Per Acquisition (sometimes Cost Per Action) is what you actually paid per conversion. It can apply to ad spend (cost per ad-driven conversion), or to fully-loaded marketing spend (closer to CAC). Most ad platforms report CPA as ad-driven only.
How to calculate
CPA = Ad Spend / Conversions.
Example: $10,000 spend / 50 conversions = $200 CPA.
Why it matters
CPA is the metric Smart Bidding (Target CPA) optimizes around. It's the input to channel-level efficiency comparison: paid search CPA vs paid social CPA tells you where the next dollar goes. Combined with conversion value, CPA tells you if a channel is profitable.
Frequently asked questions
Is CPA the same as CAC?
Not exactly. CPA usually refers to a specific platform's ad-driven cost-per-conversion. CAC is fully loaded — all marketing + sales costs / new customers.
What's an acceptable CPA?
Depends on LTV. A $500 CPA on a $5,000 LTV is healthy (10:1). A $500 CPA on a $400 LTV bleeds money fast.
Why is my CPA different across platforms?
Different audiences, intent levels, conversion definitions, and attribution windows. Compare apples to apples — same conversion event, same lookback.
