CPA = ad spend ÷ conversions recorded
$1,200 ÷ 48 = $25
Who decides what an acquisition is?
You do, when the conversion is set up. Google Ads shows CPA in the column called Cost / conv., and Meta shows it as cost per result, where the result is whatever the campaign's objective counts. If the conversion is a purchase, CPA is close to a real cost per customer. If it is a trial booking, a form, or a tap on the phone number, CPA is the cost of a step on the way to a customer, and the step can be cheap for reasons that have nothing to do with sales.
So the first question about any CPA is what sits underneath it. Two campaigns with the same CPA can be buying very different things.
What are three CPAs for one Townsville swim school campaign? (example figures)
A swim school in Townsville spends $1,200 a month on Meta ads offering a free trial lesson. The same month gives three different CPAs, depending on which action is counted as the acquisition.
| What counts as the acquisition | Count | CPA |
|---|---|---|
| Trial lesson booked (what Meta was told to count) | 48 | $25 |
| Family turned up to the trial | 26 | $46 |
| Family enrolled for the term | 10 | $120 |
The account shows $25, and that was the figure the owner had in mind when deciding whether to double the budget. The $120 is the one that pays the bills. A term of lessons is $260 a child, and most families stay for several terms, so $120 for an enrolment is a good price. It just is not the price on the screen.
There is a second cost to counting the wrong thing. Meta's delivery looks for more people like the ones who converted, so a campaign told to count trial bookings learns to find people who book trials, including the ones who forget. Sending enrolments back from the booking system as the conversion, once there are enough of them, points the campaign at families who sign up.
What happens when you hand Google a CPA target?
Target CPA is one of Google Ads' Smart Bidding strategies: you name the cost per conversion you want and Google sets each bid to get as many conversions as it can at or below it (Google Ads Help, About Target CPA bidding). Google will chase whatever conversion you gave it. Point it at trial bookings and it will find cheap trial bookings, including the ones that never enrol. A target is only as good as the conversion it is aimed at.
What do the CoraVision dashboard cards say about CPA?
The CoraVision dashboard's Google Ads and Meta cards each show the last 7 days of cost per acquisition, read from your connected accounts every night, beside your sales (or your leads, if you win work through enquiries). That figure is only as honest as the conversion beneath it, which is the whole lesson of the swim school's three rows. CoraVision never changes a bid or a target in your account; when a conversion needs redefining, you make that change yourself, with Cora pointing at where it is set.
Questions
What is the difference between CPA and CAC?
CPA is the ad account's number: its own spend divided by the conversions its tracking caught. CAC is the whole business's number: every cost of winning customers, divided by the customers who signed up. CPA is for comparing campaigns. CAC is for deciding whether winning customers pays.
Why does my CPA jump around from week to week?
Small numbers. A campaign with 4 conversions one week and 7 the next has the same spend and a CPA that drops by almost half, without anything changing. Judge CPA over a month, or until one extra conversion barely moves it, before you act on it.
Does CPA mean cost per action or cost per acquisition?
Both, and they are the same sum. Google Ads uses cost per action in its Target CPA bidding strategy, because the action can be anything you track. Owners tend to say acquisition because the action they care about is winning a customer.