Cost per action, or CPA – sometimes referred to as cost per acquisition – is a metric that measures how much your business pays in order to attain a conversion. Generally, your CPA will be higher than your cost per click, or CPC, because not everyone who clicks your ad will go on to complete your desired action, whether it’s making a purchase or filling out a form to become a lead. Cost per action takes into account the number of ad clicks you need before someone converts – in order words, improving your conversion rate will lower your CPA.
So, what determines your CPA? Like most things PPC, your CPA is directly affected by your Quality Score, Google’s all-important metric based on the quality of your keywords, ads, and landing pages. In general, the higher your Quality Score, the lower your costs – in fact, for each point your score is above the average Quality Score of 5, your CPA will drop about 16%.
Keeping your Quality Score high and your CPA low can be a huge benefit to your PPC budget over time, giving you the opportunity to buy more exposure in the online advertising space and optimize the number of conversions that come from your ad spend.
How Quality Score Affects Cost Per Action
It’s well known that AdWords Quality Score affects your cost per click, but not everyone realizes that Quality Score is every bit as important in determining your cost per conversion
When you plot average CPA against impression-weighted Quality Score, you see a strong correlation: The higher the Quality Score, the lower the cost per action.
In other words, optimizing for Quality Score and optimizing for CPA are essentially the same thing.
The below table shows how much you’ll save on cost per action if your Quality Score is higher than 5:
Likewise, having a below average Quality Score will increase your CPA, relative to your competitors, which hurts your overall ROI.
What Is Cost Per Action Bidding?
CPA bidding is a method of paid advertising that allows you to tightly control your advertising spend. Rather than paying Google for every time someone clicks on one of your ads (as with CPC bidding), CPA bidding only requires you to pay for each conversion, a metric you define yourself when you set up each campaign. This action might be a sale, a lead, a download, or some other conversion you define. CPA advertising can help you avoid spending money on search terms that may not be directly driving business. If one of your ads displays in a SERP and does not match up with the searcher’s intent, you’ll only pay if the searcher engages with the ad and ultimately converts.