CPA (Cost per Acquisition) is the average amount you pay for a single conversion. Depending on your goal, that conversion is a lead, a purchase, a sign-up or a booked call.
How is CPA calculated?
CPA = ad spend / number of conversions
You decide which conversion counts. For lead generation it is usually a submitted form, for a shop a completed purchase.
Example
You spend 3,000 euros a month on Google Ads and get 60 inquiries through your contact form.
CPA = 3,000 € / 60 = 50 €
Each lead costs you 50 euros. If one in five leads turns into a customer, your cost per new customer is 250 euros. Whether that is good depends on what a customer is worth to you.
Why does CPA matter?
CPA is the core metric for anyone generating leads rather than direct sales: agencies, service businesses, B2B companies. It shows at a glance which campaign is efficient. Google Ads and Meta also use it for bid strategies such as "Target CPA" or cost caps.
But your CPA is only as good as your conversion tracking. When signal loss keeps some leads from reaching the platform, your CPA looks worse than it is, and the algorithm shows your ads to the wrong people. Naming events properly matters too, for example using Meta's standard events like "Lead" or "Purchase", so the platform knows what to optimize for.
Where ROAS looks at revenue, CPA only looks at cost. For proper attribution, meaning which channel delivers the cheapest leads, you also need reliable source data for every lead.
CPA with LeadSignal
LeadSignal detects forms automatically and lets you mark conversions with a click in the visual event setup, with no developer and no Google Tag Manager. You can map each event to a platform event such as "Lead" and send it to Meta, Google Ads, LinkedIn and TikTok. The lead list shows source, click ID and landing page for every lead, so you know which campaign brought in which lead. Our article on ad tracking for agencies shows how this works across multiple clients.
If you want to go beyond cost per lead and see cost per won customer based on your CRM data, our sister product LeadMetrics is the right tool.