CPA stands for cost-per-acquisition.
Quite simply put, it is the marketing cost of a sale. In order to track a CPA you will need to have installed the correct e-commerce tracking options for your website.
Using AdWords conversion tracking, you’ll see two columns in your reports (you may need to edit your columns to see this).
The cost per converted click column equates to your CPA.
It may be that this figure is much higher than you were expecting, or hoped. It is worth remembering though, that this does not take into account any phone sales generated (should you take orders by phone, then call-tracking is advisable).
It also doesn’t take into account cross-device conversions i.e. someone initially finds and browses your site on their mobile device, then make the purchase using a laptop, PC or tablet. This is where the second column, estimated total conversions comes in.
From Google AdWords
Cost per converted click
Cost/converted click is your cost divided by your total converted clicks.
What it means: This is how much you pay, on average, for each click that can be tracked to a conversion during your chosen conversion window.
Why to use it: This ratio can help you understand your return on investment in each converting customer.
Estimated total Conversions
This is our best estimate of the total number of conversions that AdWords drives.
What it means: Estimated cross-device conversions are counted when a customer clicks an ad on one device, then converts on another device.
What it includes: Estimated conversions include cross-device, many-per-click and phone call conversions. If there isn’t enough data for an estimate, then this column will equal the Conv. (many-per-click) column.
Why use it: You can use this column to understand your return on investment and make better decisions about your bids and budgets.