Contents
- CPA divides ad spend by the number of conversions recorded over the same period.
- It says nothing about profitability until you compare it to the margin one conversion generates.
- A badly calibrated target CPA is the number one reason automated bidding campaigns stall.
Definition
CPA, cost per acquisition, measures what one conversion costs on average. Depending on the account, a conversion means a purchase, a form, a call or any action declared as such.
Formula
CPA = total cost divided by number of conversions, over the same period and the same attribution window.
Worked example
A campaign spends €3,200 in a month and records 64 forms. CPA is €50. If one form in five turns into a customer and brings in €600 of margin, the real cost of acquiring a customer is €250 for €600 of margin: the campaign is profitable.
Orders of magnitude
There is no good CPA in absolute terms: it depends entirely on what a conversion is worth. Our piece on the Google Ads metrics clients actually read covers how to present it in a client meeting. In B2B lead generation, CPAs of €50 to €200 are common; in e-commerce, you reason in CPA against average order value instead. The only useful benchmark is your own history.
The most common mistakes
- Comparing CPA across two accounts or two sectors. A CPA of €80 can be excellent or disastrous depending on what the conversion is worth.
- Mixing conversion actions. If the account counts both form submissions and contact page views, the average CPA means nothing.
- Setting the target CPA too low at launch. The algorithm then restricts delivery to the point of no longer collecting enough data to learn.
Where to find the metric
In Google Ads, the Cost per conversion column, available at every level. In Meta, the Cost per result column, which follows the campaign objective. In LinkedIn Ads, the Cost per result or Cost per lead column depending on the format. In GA4, you have to calculate it: imported cost divided by key events.
Frequently asked questions
The Adwise team connects Google Ads, Meta Ads, LinkedIn Ads, GA4 and Search Console so agencies and freelancers can run their campaigns from a single place.