CPA

What is CPA?

CPA stands for Cost Per Acquisition. It measures what it costs to acquire a conversion — a purchase, a lead, a signup. The formula: total ad spend divided by number of conversions. It's the inverse perspective of ROAS: instead of revenue per dollar, you see cost per result.

What it means in practice

In practice, CPA is the clearest way to understand what your conversions actually cost. It makes it easier to set caps and budget rules. If your average order value is $100 and your margin is 40%, you know your CPA can't exceed $40. CPA should be broken down by channel, campaign, and segment to be useful. An average hides more than it shows. I use CPA as the starting point for every budget conversation.

Why it matters

CPA gives a direct link between ad spend and business outcome. It makes budget decisions concrete. You can answer the question "what does it cost to acquire a customer?" — and that's a question the board, CEO, and CFO understand.

Common mistakes

• Measuring CPA at the click level instead of actual business outcomes
• Setting a CPA target without connecting it to margin and LTV
• Optimizing for lowest CPA instead of best customer quality