CPA: definition
Cost per acquisition: what a targeted action (a lead, a signup, a sale) costs you on a given paid channel.
By Isidore Mikorey-Nilsson · June 14, 2026
Definition
CPA (cost per acquisition) measures the cost of a specific conversion on a channel, most often a paid one. Depending on what you count as an "acquisition" (a lead, a trial, a paying customer), the number changes completely, so you always need to specify the action being measured. It is the day-to-day steering tool for a paid campaign.
How to calculate it
CPA = campaign spend / number of conversions
Why it matters
CPA lets you optimize a campaign in real time: you immediately see which targeting or which ad costs you the least per conversion. But a low CPA on worthless leads is meaningless: it must always be read in light of the quality of what you're acquiring.
When to use it
You track it campaign by campaign to arbitrate ad budgets. In practice, you clearly define the action being measured, you compare the CPA to the average revenue that action brings in, and you cut what costs more than it earns.
Example
A campaign that spends 500 euros to generate 25 trial signups shows a CPA of 20 euros per signup.
Common mistakes
- Confusing it with CAC.
- Optimizing a low CPA on worthless leads.
- Not specifying the action being measured.
Don't confuse it with
- cac: CPA covers a specific action on one channel (often a lead); CAC aggregates the total cost of landing a paying customer, across all channels.
What our data says
Related terms
Articles that use this term
Frequently asked questions
- Are CPA and CAC the same thing?
- No: CPA measures the cost of a specific conversion on one channel, CAC the total cost of turning a stranger into a paying customer. The two are often confused.