CPA calculator for any conversion, with the gap to your target

Cost per acquisition is the price of one completed action, and the action is whatever you are paying the platform to produce: a purchase for e-commerce, a lead for a B2B site, a trial for SaaS, an install for an app, a booked call for a sales team. That flexibility is why CPA is the metric ad platforms bid on. Google's Target CPA and Meta's Cost Cap take a CPA and work backwards to a bid.

It sits between cost per lead, which is always a lead, and customer acquisition cost, which is always a paying customer. Use CPA when the conversion you optimise for is neither, or when you run several conversion types and want one word for the metric.

A €100 CPA is a bargain if the action brings in €500 and a loss if it brings in €40. The formula is the easy part. The judgement comes from your unit economics: revenue per action, gross margin, and how much of that margin you are willing to spend on growth. That is what a target CPA is, the ceiling those three numbers allow, and it is what the calculator compares your actual CPA against.

The comparison tells you two things: how far over or under the ceiling you are per action, and what the same spend would have produced at target. The second number is the one to bring to a budget meeting. "We got 100 purchases; at target CPA the same budget buys 125" is a sentence people act on.

In order of leverage:

• Tracking. Automated bidding learns from the conversions it can see. If the pixel misses 30 to 40 percent of them, the platform optimises towards the visible subset and your real CPA is a third lower than the dashboard says. Fixing the feed often drops reported CPA more than any campaign change.
• Conversion rate. Doubling the landing page from 2 to 4 percent halves CPA on the same media plan, with no change to bids or audiences.
• Creative and audience. Better hooks raise click-through, which lowers CPC, which lowers CPA proportionally. Real, but the smallest of the three.