Written by Krisztián Stark
Key takeaways
- CPA = ad spend divided by the number of completed actions, and the action must be defined before the number means anything.
- CPL, CPI, CPS, and CPE are all kinds of CPA, each named after the action being paid for.
- A good CPA is the value of one action divided by your target ROAS. Anything above that loses money, however cheap it looks.
What is CPA (cost per action)?
CPA, or cost per action, is what you pay for one completed action that you care about, such as a sign-up, an install, or a purchase. You calculate it by dividing your ad spend by the number of those actions. As a pricing model, CPA means the advertiser pays only when the action happens, not for views or clicks.
You will also see CPA expanded as cost per acquisition. The math is the same. “Acquisition” usually hints that the action is a new customer, while “action” can be any step you define. Whichever word a report uses, check what was counted.
The CPA formula
CPA = ad spend ÷ number of actions.
If you spend $400 and get 80 sign-ups, your CPA is $5.00.
When you buy clicks instead of actions, the same number comes from your conversion rate: CPA = CPC ÷ conversion rate. When you buy impressions, it is CPA = CPM ÷ (1,000 × click rate × conversion rate). These two lines are how you turn any price tag into a cost per result.
Quick math: from a click price to a CPA
You pay $0.30 per click and 4% of visitors create an account. Your CPA is $0.30 ÷ 0.04 = $7.50. If a clearer landing page lifts the conversion rate to 6%, the CPA falls to $5.00 without any change in the click price. The rates are illustrative, not benchmarks.
CPA as a metric vs CPA as a pricing model
The term is used in two ways, and mixing them up causes a lot of confusion.
- As a metric, CPA is something you calculate after the fact for any campaign. A search campaign billed per click still has a CPA: total spend divided by the sales it produced.
- As a pricing model, CPA is how the campaign is billed. You agree on a price per action in advance, and the channel is paid only when an action is confirmed. Affiliate programs, offerwalls, CPA networks, and many app install deals work this way.
There is a middle ground too. Some auction platforms let you bid toward a CPA while still charging per click or impression. Google Ads, for example, describes Target CPA as an automated bid strategy where you set your desired average cost per conversion and it sets bids based on how likely each ad is to convert. Your average may land near the target, but you still pay for the clicks, so the risk of a weak landing page stays with you.
CPA vs CPL, CPI, CPS, and CPE
Most “cost per” terms are CPA with a specific action in the name:
| Term | The action | Typical use |
|---|---|---|
| CPL, cost per lead | A sign-up or form with contact details | B2B, newsletters, services |
| CPI, cost per install | An app is installed and opened | Mobile app growth |
| CPE, cost per engagement | An interaction or in-app goal | Social, apps, games |
| CPS, cost per sale | A completed purchase | Online stores, affiliate programs |
Three of them have full guides: cost per lead, cost per install, and cost per engagement. The deeper the action, the higher the price per result and the less you pay for people who never come back. For how CPA compares with paying per view or per click, read CPM vs CPC vs CPA.
What is a good CPA?
There is no universal good CPA. A $40 CPA is excellent for a product that earns $400 per customer and a disaster for one that earns $20. The useful question is how much one action is worth to you.
Target CPA = value of one action ÷ target ROAS.
- Estimate the value of one action. For a sale, use the revenue it brings. For a sign-up or install, use the share that later pays multiplied by what they pay.
- Pick a target ROAS. A ROAS of 2 means you want $2 back for every $1 spent. What is ROAS? explains how to find your break-even point.
- Divide. The result is the most you should pay per action and still hit your target.
Illustrative example: a subscription app
One in ten users who finish onboarding later subscribes, and a subscriber brings $60 in revenue over their first year. Each onboarded user is worth 0.10 × $60 = $6.00. With a target ROAS of 3, your target CPA is $6.00 ÷ 3 = $2.00 per onboarded user. Any channel that delivers onboarded users below $2.00 meets your goal. These figures are made up for the arithmetic, so use your own.
If you want to plan around profit over a customer’s lifetime instead of first-year revenue, CAC vs CPA vs LTV shows how.
Common CPA mistakes
- A vague action. “Sign up” can mean an email typed into a box or a verified account. Write down exactly what counts and how it is confirmed before you compare prices.
- Comparing CPAs for different actions. A $1 install and a $15 purchase are different products. Compare channels on the same action.
- Stopping at the action. A low CPA from users who leave the next day can be worse than a higher one from users who stay. Track what happens after the action, too.
- Judging too early. With five results, one lucky or unlucky day swings the CPA a lot. Wait for enough actions before you cut or scale.
- Mismatched windows. One report may count actions up to 30 days after a click, another only 7 days. Compare reports with the same conversion window.
- Forgetting fraud. When you pay per action, fake actions become the thing to fake. Pick actions you can verify, and read Ad fraud and bot traffic.
Paying per action on Sharklio
Sharklio is built around CPA pricing. In a task campaign, users complete the action you describe, such as signing up, joining a community, or reaching a level in your app, and send proof. You review each completion and pay only for the ones you approve. You set the price per result for each country yourself, from $0.01, so you know your CPA before the campaign starts. Multi-step offer campaigns, available by arrangement with our team, pay for each step your own server reports through a postback. You can create a free account and your first campaign today. A good first test: take the target CPA you worked out above, set it as your bid in two or three countries, and see which ones deliver at that price.
Frequently asked questions
What does CPA stand for in marketing?
Cost per action, also called cost per acquisition. It is the cost of one completed action, such as a sign-up, an install, or a sale.
How do you calculate CPA?
Divide your ad spend by the number of actions. $250 spent for 50 sign-ups is a CPA of $5.00.
Is cost per action the same as cost per acquisition?
The formula is the same. “Acquisition” usually means a new customer, while “action” can be any step you choose, such as a lead or an install.
What is a good CPA?
One below the value of the action divided by your target ROAS. Industry averages are a poor guide because the value of an action differs so much between businesses.
What is the difference between CPA and CPC?
CPC is the price of a click, CPA is the price of a completed action. You can turn a CPC into a CPA by dividing it by your conversion rate.
Why is my CPA going up?
Usually because the conversion rate fell, the click or impression price rose, or the traffic mix shifted to more expensive countries or placements. Check each of those before changing the offer itself.
