What is Cost Per Action (CPA)?

Cost Per Action (CPA) is a pricing and performance metric that tells you how much you're spending for each desired action a user takes, like signing up, starting a trial, or completing a purchase.

For example, if you spend $1,000 on ads and get 50 trial signups, your CPA is $20.

It’s more specific than CPI (Cost Per Install) because it’s tied to actual value-driven behaviors after the install.

How does it work?

The formula is:

CPA = Total ad spend ÷ Number of actions completed

What counts as an “action” depends on your campaign objective. Common examples include:

• Trial starts

  
  

• First purchase
  
  

• Subscription initiated
  
  

• Onboarding completed
  
  

• Add to cart
  
  

CPA is usually set as a goal in UA campaigns. Some ad networks (like Meta or Google) even optimize delivery toward hitting a target CPA.

You can also calculate CPA manually by channel, campaign, creative, or audience to compare performance.

Why it matters

CPA gives you a more realistic view of how much it costs to acquire value, not just clicks or installs.

It helps you evaluate if your campaigns are profitable, especially when paired with LTV or ARPU. If your CPA is higher than the value you’re getting from users, something needs fixing.

Smart teams use CPA to:

• Optimize funnel performance (e.g., install → action)
  
  

• Set ROAS targets
  
  

• Compare channels fairly
  
  

• Scale what’s working profitably
  
  

CPA is where growth meets economics, and it’s one of the most important metrics to watch when investing in paid growth.