CPA connects ad spend directly to the result you care about. Where CPM and CPC tell you what attention and traffic cost, CPA tells you what an outcome costs, which is why most performance campaigns are optimised against it.
How Do You Calculate CPA?
The formula is: CPA = ad spend / conversions.
If a campaign spends $2,000 and produces 50 purchases, the CPA is $40. The same campaign could have a different CPA for different actions: $8 per add to cart, $40 per purchase.
What Is a Good CPA?
A good CPA is one you can afford, and that depends on what each conversion is worth. For a one time purchase, your maximum CPA is roughly the gross profit per order. If customers buy again, you can afford more, up to a sensible share of LTV. A $40 CPA is excellent for a product with $100 of profit per order and a loss for one with $25.
CPA vs CAC
CPA usually counts only ad spend and the conversions an ad platform attributes to it. CAC counts all the costs of winning a new customer, including tools, team and agency fees, across every channel. CPA steers campaigns; CAC tells you whether customer acquisition as a whole is profitable.
How to Lower CPA
- Improve the landing page and checkout, since a higher conversion rate lowers CPA without touching bids.
- Tighten targeting and exclude audiences that click but never buy.
- Refresh creative when CTR drops, before rising CPMs push CPA up.
- Make sure conversion tracking is accurate, so the platform optimises toward real results.
Frequently asked questions
What is CPA in marketing?+
CPA is cost per acquisition, the average amount of ad spend needed to get one conversion such as a sale, lead or sign-up.
How is CPA calculated?+
Divide ad spend by the number of conversions. For example, $2,000 of spend and 50 purchases gives a CPA of $40.
What is the difference between CPA and CAC?+
CPA covers ad spend per conversion, often for one channel. CAC covers all acquisition costs, including tools and team, per new customer across every channel.