Cost per acquisition (CPA) is ad cost divided by the number of conversions it produced. Ad platforms call it cost per conversion. It is narrower than customer acquisition cost (CAC), which counts all sales and marketing costs per new customer. In SaaS, CPA usually measures the cost of a lead or trial, and the gap between that and a paying customer is where most of the analysis happens.
How to calculate it
CPA depends entirely on what you count as a conversion, so name the conversion every time you quote it.
CPA = Ad spend / Conversions
Example: $3,000 / 20 demo requests = $150 per demoCPA at each funnel stage
A demo CPA can look healthy while the cost per qualified opportunity is poor, if most demos are students, competitors or tiny teams. SaaS teams that import CRM stages back into the ad platforms can see CPA for each stage and judge campaigns by the one closest to revenue they have enough data for.
- Cost per lead or trial: fast feedback, weak signal of quality.
- Cost per qualified lead or opportunity: slower, much stronger signal.
- Cost per customer: the real answer, but often too slow and sparse for day-to-day optimization.
Setting a target
A sensible CPA target works backward from customer value. If you know roughly what a customer is worth and what share of demos become customers, you can work out what a demo can afford to cost. Platforms will then bid toward that number with target CPA strategies.
Example
Two campaigns, two stories
Hypothetical company Marlowgate sees a cheaper demo CPA on a broad category campaign than on its competitor-alternative campaign. After importing opportunity stages from its CRM, it finds the alternative campaign produces far more qualified opportunities per dollar, and shifts budget accordingly.
Common mistakes
Mixing conversion types
Counting newsletter sign-ups and demo requests as the same conversion makes CPA meaningless. Set a primary conversion and mark the rest secondary.
Questions
No. CPA covers ad spend per conversion for a campaign. Customer acquisition cost includes salaries, tools and all channels, divided by new customers.
