CPA
cost per actionCPA (cost per action) tells you what one conversion costs in advertising. The conversion can be a sale, a lead or a booking, and CPA is calculated by dividing ad spend by the number of conversions. If 1,000 € of spend produces 20 sales, the CPA is 50 €.
Good to know
Alongside ROAS, CPA is the most important steering metric in paid advertising, and it fits especially well when order value is stable or the sale closes later. Always compare CPA against the value of the conversion: a 50 € CPA is cheap for a 500 € sale and unsustainable for a 60 € one. In B2B its natural companion is CPL, the cost per lead.
The CPA a platform reports and your own books often differ, because Meta and Google read conversions through their own attribution models. Tie decisions to one source of truth, usually GA4 or your own system.
FORMULA
How CPA is calculated
CPA is ad spend divided by the number of conversions. Pick a conversion that matters to the business, not a click.
CPA = ad spend ÷ conversions
Ad platforms optimise towards your CPA target automatically, so the target level directly steers who sees your ads.
EXAMPLE
One sale cost 50 euros. Whether that is profitable only becomes clear against the margin of the sale.
PITFALLS
Two ways to misread CPA
The conversion is loosely defined
If a newsletter signup and a sale count as conversions in the same campaign, CPA looks fine but says nothing. One campaign, one conversion goal.
View-through conversions inflate the number
A view-through conversion is logged even though the user only saw the ad. Separate click and view-based conversions in reporting.
Seasonality is read as a trend
CPA moves with the seasons: an expensive January conversion does not mean a broken campaign. Always compare against the same period last year.
FREQUENTLY ASKED
Frequently asked questions
What is a good CPA?+
One that leaves margin: calculate the profit of a sale or a customer relationship and subtract your target profit. Comparing across industries misleads.
What is the difference between CPA and CPL?+
CPL measures the price of a lead, CPA the price of whichever conversion you chose. If the conversion is a sale, the difference is large: leads come far cheaper than sales.
Why does CPA rise when the budget grows?+
The platform first shows ads to the audience most likely to convert. A bigger budget expands into colder audiences, so the average price rises.
How do I set a CPA target on the platform?+
Start from your realised average and tighten it 10–20 % at a time. A target set too tight from day one stalls delivery completely.
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Maintained by the VSCY editorial team · Updated 6 Aug 2026 · Part of the marketing glossary (99 terms)
