What is CPA, and how do you optimize it?
Cost per acquisition (CPA) is your advertising spend divided by the number of completed actions you care about, such as sign-ups, trial starts, bookings, deposits or app installs. It tells you what each customer action costs you, whatever the ads were bought on.
The formula
CPA = spend ÷ acquisitions, and CPA = CPC ÷ conversion rate when you buy on CPC.
Define the action precisely
"Acquisition" should mean one specific, verifiable event: an account created, a booking confirmed or a first deposit made. Send it once per user, with your own order or user ID, so duplicates can be removed.
How to improve CPA
- Track every step: click → landing page view → form start → completed action. The biggest drop is usually where to work first.
- Remove placements and audiences with spend and no actions once there is enough data to be confident.
- Test one change at a time (a creative, a landing page or a country) with a clear hypothesis and enough sample to trust the result.
- For apps, connect your mobile measurement partner so installs and in-app events are reported server to server (CPI is CPA for installs).
Common questions
Is CPA the same as CPL?
CPL counts leads (a person showing interest). CPA counts a completed action such as a purchase, booking or sign-up. Many businesses track both.
Should I pay per acquisition?
On Instant Metric you pay CPC or CPM and set CPA as your goal. That keeps billing simple and transparent while optimization still aims at the result you care about.