Metric note

Cost per acquisition (CPA): formula, examples and calculator

Cost per acquisition (CPA) is advertising spend divided by the number of acquisitions it produced: the average cost of one counted outcome, such as a lead, a sign-up or a purchase. If a campaign spends 900 and records 30 completed enquiries, its CPA is 30.00 per enquiry in the account currency. The name is used loosely, so always state which action the denominator counts. Different actions give very different CPAs for the same spend.

By Adlane · Updated 29 October 2026

CPA formula with a worked example

Take spend and the count of one named action from the same report: one account currency, one complete date range, the same campaign or ad set, and a visible conversion window. Divide spend by the count. Rearranged, the same relation gives the budget needed for a target number of acquisitions at a given CPA.

Worked example (illustrative numbers): 900 spend ÷ 30 completed enquiries = a CPA of 30.00. At that CPA, 50 enquiries would need about 1,500 of spend. A break-even CPA is the gross profit one acquisition brings in before advertising costs: if a sale earns 120 of gross profit, any CPA above 120 per sale loses money on that sale.

CPA = ad spend ÷ acquisitionsSpend needed = target CPA × acquisitionsBreak-even CPA = gross profit per acquisition before ad costs

Free tool · runs in your browser

Calculate CPA, budget or conversions.

Choose what to solve for, then enter the other numbers. The starting values are illustrative. Nothing you enter is sent to Adlane.

Which action does your cost per acquisition count?

Write a plain-language definition of the action before calculating anything: “a submitted enquiry form that reached the inbox” is different from “a click on the contact button”. In Google Ads, the Conversions column includes the conversion actions marked as primary, so check which actions those are and whether any count the same outcome twice. In Meta, the Results column follows the optimisation event chosen for the ad set.

Illustrative example: a campaign spends 900 and records 30 completed enquiries. The sales team qualifies 10 and closes 3. The same spend gives 30.00 per enquiry, 90.00 per qualified enquiry and 300.00 per new customer. Only the last is a customer acquisition cost.

Counted action (illustrative)	Spend	Count	CPA
Completed enquiry	900	30	30.00
Qualified enquiry	900	10	90.00
New customer	900	3	300.00
Purchase (none recorded)	900	0	Unavailable

CPA vs CPC vs CPM vs CAC

All four divide cost by a different count, so each answers a different question. CPA in ad platforms usually covers media spend only; customer acquisition cost (CAC) in finance usually includes sales and marketing costs beyond ads, divided by new customers.

Metric	Formula	Question it answers
CPA (cost per acquisition)	Ad spend ÷ counted actions	What did one counted outcome cost in media?
CPC (cost per click)	Ad spend ÷ clicks	What did one recorded click cost?
CPM (cost per mille)	Ad spend ÷ impressions × 1,000	What did 1,000 impressions cost?
CAC (customer acquisition cost)	Sales and marketing costs ÷ new customers	What did one new customer cost the business?

Where to find CPA in Google Ads and Meta Ads Manager

Google Ads: in the campaigns table, open Columns and add Cost, Conversions and Cost / conv. (cost per conversion, the platform’s CPA). Target CPA bidding uses the same definition. In the Google Ads API the field is metrics.cost_per_conversion, returned in micros, so divide by 1,000,000. Check the conversion actions included before comparing campaigns.

Meta Ads Manager: Cost per result divides amount spent by the result of the ad set’s optimisation event, so it can mean cost per purchase in one row and cost per lead in another. For a fixed action, add a specific column such as Cost per purchase or Cost per lead. In the Insights API, cost_per_action_type lists the cost for each action type.

When is CPA undefined, and why do recent values change?

A zero-outcome denominator makes the ratio undefined. Show it as unavailable, not as zero: a row with spend and no outcomes is the most expensive row in the report, not the cheapest. This is common for new campaigns and for short or recent periods.

Recent CPA values are also provisional. Conversions attributed to a click can be recorded days later, so the last week of any report will usually show a higher CPA than it will after the window matures. Note the window and the report date rather than comparing a fresh week with a settled month.

Why a cheaper form submission is not a cheaper customer

Two campaigns can report identical CPA while one attracts job seekers and the other attracts buyers. The ratio contains no information about quality. Pair it with downstream records such as qualification rates or order values, and with the search terms or placements that produced the actions.

Resolve measurement and qualification questions before ranking campaigns by CPA. A ranking built on a mixed set of conversion actions, or on actions that fire twice, will reward the wrong campaign.

How to review cost per acquisition in Adlane

Connect the relevant Google Ads or Meta account, then ask a bounded question that names the action: “For the last complete month, show spend, completed enquiry conversions and cost per enquiry by campaign in the account currency, with the conversion window noted.” Review the evidence rows and check which conversion actions were included.

Proposed changes, such as shifting budget towards a lower-CPA campaign, are prepared as proposals for your approval and are never applied by the conversation.

Questions, answered

What is cost per acquisition?

Cost per acquisition (CPA) is the average ad spend for one counted outcome, such as a lead, sign-up or purchase. It is ad spend divided by the number of those outcomes.

How do you calculate CPA?

Divide ad spend by the number of acquisitions in the same period and scope. 900 spend ÷ 30 enquiries = a CPA of 30.00 per enquiry.

What is the CPA formula?

CPA = ad spend ÷ acquisitions. Rearranged, the spend needed for a target is target CPA × acquisitions.

What is a good CPA?

One below your break-even CPA: the gross profit an acquisition brings in before ad costs. There is no universal benchmark, because value per acquisition differs by business.

Is CPA the same as CAC?

Not usually. CPA in ad platforms counts media spend per counted action. Customer acquisition cost counts all sales and marketing costs per new customer.

Why does my CPA show as unavailable?

With zero acquisitions the ratio is undefined. Showing zero would wrongly make the row look like the cheapest when it spent money for no outcome.

Free CPA calculator

Need the arithmetic only? The CPA calculator runs in your browser with the formula shown: CPA = spend ÷ completed actions.