What is CPA?
CPA, or cost per acquisition (also called cost per action), is what you pay in ad spend for each conversion. A conversion is whatever you are optimizing for: a purchase, a lead, a signup or an app install. In Meta Ads Manager it appears as "cost per result", and for a sales campaign that is your cost per purchase.
CPA is the metric closest to profit, because it compares what you spend with what you actually got. CPM, CPC and CTR explain why your CPA is what it is.
The CPA formula
Use "Find ad spend" above to budget for a sales target, or "Find conversions" to estimate what a budget will bring in.
Worked example
You spent $1,000 and got 25 purchases.
Planning: to get 60 sales at a $35 CPA, you need about 60 × $35 = $2,100 in ad spend.
Your max CPA: the number that matters
A CPA is only good or bad compared with what each sale earns you. Your break-even CPA (max CPA) is your profit per sale before ad spend:
Pay more than $32 per sale in that example and every order loses money. The ROAS calculator works out your max CPA and break-even ROAS from your price and costs, and the profit margin calculator shows the margin behind it.
If customers buy from you again, you can afford more than the first order's profit. Use the LTV calculator to see what a customer is worth over time.
Where your CPA comes from
CPA breaks down into the steps before the sale, which tells you which one to fix:
- High CPM: impressions are expensive (audience, season, placement).
- Low CTR: the creative is not earning clicks.
- Low conversion rate: the landing page, price or offer is not closing the sale.
Example: a $1.00 CPC with a 2.5% conversion rate is a $40 CPA. Lift the conversion rate to 4% and the CPA drops to $25 with the same ads.
CPA vs CAC
CPA is usually measured per campaign and counts every conversion the ad platform attributes to it, including repeat buyers. CAC (customer acquisition cost) is broader: what it costs to win one new customer across all your marketing, sometimes including agency fees, tools and creative production. CAC is the number to compare with lifetime value; CPA is the one you manage day to day in Ads Manager.
How to lower your CPA
- Test new creatives: a better hook lifts CTR, which lowers CPC and CPA together.
- Fix the landing page before raising budgets; conversion rate often moves CPA more than the ads do.
- Optimize for the event you actually want. A campaign optimized for clicks finds clickers, not buyers.
- Give ad sets enough conversions to learn. Meta says an ad set needs about 50 optimization events in a week to leave the learning phase, and performance is usually less stable until then.
- Raise order value with bundles or offers so each acquisition is worth more.