- The CPA formula, with a worked example
- How Google Ads Target CPA works
- The catch: a target that's too low cuts your results
- Why your results won't match the number you typed
- Bid limits, budget and Display
- Recent Target CPA changes, as of October 2026
- How to set a sensible Target CPA
- What CPA can and can't tell you
- Frequently asked questions
In marketing, CPA stands for cost per acquisition, sometimes called cost per action: it's what you spend, on average, to get one conversion, such as a sale, a lead, a sign-up or an app install. You work it out by dividing what you spent by the number of conversions you got.
If you've landed here wondering about accountants, that's the other CPA, and this page isn't about that. It's also not about CPA as an affiliate commission model. This is the ad metric, and how Google Ads uses it when you ask it to bid for you.
The CPA formula, with a worked example
The sum is simple:
CPA = total ad cost divided by number of conversions
Say a campaign got 30 conversions over the last 30 days, and it cost $300 in that period. Your CPA is $300 divided by 30, which is $10. Every conversion cost you $10 on average. Some cost more and some cost less, which is why it's always an average, never a fixed price. (Figures here are an illustration, as of October 2026, built around Google's own $10 example.)
| Term | Plain meaning | What Google says |
|---|---|---|
| CPA | Cost per acquisition or action | Your average cost per conversion |
| Target CPA | The average you ask Google to aim for | Needs conversion tracking set up first |
| Average target CPA | The traffic-weighted target Google optimised for | Compare your achieved CPA with this |
| A target set too low | Google skips clicks that might have converted | You get fewer total conversions |
How Google Ads Target CPA works
Google defines Target CPA (it uses 'cost per action') as an automated bid strategy that sets bids to get as many conversions as possible. You set the average cost per conversion you want, and Google Ads sets bids based on how likely each ad is to convert. In App campaigns, the same value applies to cost per install or cost per in-app action.
Google's own example: with a target CPA of $10, Google Ads sets bids to get as many conversions as possible within your budget at $10 on average. It adjusts each bid using real-time signals such as device, browser, location, time of day and remarketing list.
You must set up conversion tracking before you can use Target CPA, because Google can't aim for a cost per conversion it can't count. You don't need a conversion history to start, and Google says it's effective for campaigns of all sizes. Google is also honest that your actual CPA depends on things outside its control, like changes to your site or ads and how competitive the auction is.
The catch: a target that's too low cuts your results
This is where people trip up. It feels sensible to type in a low number and let Google work hard for it. Google warns against exactly that: setting a target that's too low may cause you to forgo clicks that could result in conversions, resulting in fewer total conversions.
So a lower target doesn't mean cheaper customers. It can just mean fewer of them. Google recommends that if a campaign has history, you start with your average CPA from the last 30 days, adjusted for conversion delay, and judge performance over the last 30 days with at least 30 conversions. If you want to try a different target without risking the live campaign, Google lets you save the change as an experiment instead.
Why your results won't match the number you typed
The second catch is in the reporting. Google says your average target CPA is a traffic-weighted average that includes device bid adjustments, ad group targets and any changes you made over time, so it can differ from the target you set. When you check results, compare your achieved CPA with the average target CPA, not with the figure you typed in. You'll find the metric in the Campaigns performance columns and the bid strategy report.
Device adjustments are a good example of why. Google says a $10 target with a +40% mobile adjustment becomes a $14 target on mobile, and a -100% adjustment stops your ads showing on mobile altogether.
Want AI doing the heavy lifting in your marketing?
I build the systems that handle the boring 80 percent, so you get your week back. Done properly, with the human kept in.
Bid limits, budget and Display
- Bid limits. Google doesn't recommend setting max or min bid limits on Target CPA, because they restrict its optimisation. Limits only apply to Search Network auctions, and only to portfolio strategies.
- Budget. Google recommends being comfortable spending up to 2 times your average daily budget, while not going over your monthly charging limit.
- Display. Display campaigns can pay for conversions instead of clicks: in the Bidding section, choose 'Pay for', then Conversions.
Recent Target CPA changes, as of October 2026
Google's help page carries three dated updates. From June 2026, the label 'Maximize conversions with a Target CPA' is changing to 'Target CPA', with no change in how bidding behaves. From August 17, 2026, Google is updating its bidding systems for budget-limited campaigns using Target CPA or Target ROAS, which may cause temporary swings in performance and traffic. And a Bid Target Adjustment Tool became available from July 6, 2026. If your numbers moved around after mid-August, that update is worth ruling out before you change anything.
On the reach side, cost per thousand impressions is the other number to know.
How to set a sensible Target CPA
- Set up conversion tracking so every conversion is counted.
- Look at your average CPA over the last 30 days.
- Start your Target CPA near that figure, not below what you can realistically win.
- Judge it over 30 days with at least 30 conversions.
- Compare your achieved CPA with the average target CPA in your reports.
- Test any new target as an experiment before changing the live campaign.
Click-through rate is the first step in the chain, so see what CTR means.
What CPA can and can't tell you
CPA tells you what a conversion costs. It doesn't tell you whether that conversion is worth it. A $10 lead is brilliant if that customer is worth hundreds to you, and a disaster if they're worth less than $10. So always read your CPA next to what a customer is worth to your business, and next to your website's conversion rate, because a page that converts badly pushes CPA up whatever you bid.
I won't give you a 'good CPA' number, because there isn't one that fits every business. Track it alongside the other sales funnel metrics worth tracking, and if you're setting up your first campaign, start with how to run a PPC campaign in Google Ads.
Frequently asked questions
What does CPA mean in marketing?
CPA means cost per acquisition, sometimes called cost per action. It's what you spend on average to get one conversion, such as a sale, lead, sign-up or install.
How do you calculate CPA?
Divide your total ad cost by the number of conversions. If a campaign cost $300 and brought in 30 conversions, your CPA is $10.
Do I need conversion tracking for Target CPA?
Yes. Google says you must set up conversion tracking before you can use Target CPA, though you can start without any conversion history.
Why is my actual CPA different from my Target CPA?
Google says your average target CPA is a traffic-weighted average that includes device adjustments, ad group targets and changes over time. Compare your achieved CPA with that average, not the number you typed.
