What is cost per acquisition (CPA)?
Cost per acquisition (CPA) is what you pay in ads for one conversion, such as a purchase or a lead. It is ad spend divided by conversions. The highest CPA you can afford on a purchase is your break-even CPA, which the break-even ROAS calculator works out from your margins.
The formula
Leave one field empty and it is worked out from the other two. With all three filled, CPA is worked out from spend and conversions. Count the same conversion event your campaign is set to.
Worked example
$1,500 brought 50 conversions, which is $30.00 for each one.
Using it on Meta ads
Use the conversion event your campaign is set to, and the same dates as the spend. If CPA rises, look one step up the funnel: a pricier cost per click or fewer purchases per click.
CPA counts every conversion, including repeat buyers. To see what a new customer costs once every acquisition cost is in, use the CAC calculator.
Questions
Whatever the campaign is set to get: a purchase, a lead, a sign-up. Use that same event here, or the CPA will not match what Meta reports.
For a purchase, it is what one order leaves after product, shipping and fees, which is the break-even CPA. Above it each sale loses money on the first order.
CPA counts every conversion an ad brings, including people who had bought before. CAC counts only new customers and often adds costs beyond ads.
