Cost per acquisition is the cost to generate one defined conversion, such as a lead, signup, or sale. You divide the total campaign spend by the number of conversions. CPA measures campaign efficiency at a specific conversion point, which is usually earlier and cheaper than winning a full customer.

CPA is a channel-level efficiency number, not a business-level one. It is useful for comparing campaigns, but do not confuse a low CPA on leads with a healthy business. Cheap leads that never close are expensive customers. Always trace CPA through to CAC before you celebrate it.

Example:

 A campaign spends $5,000 and produces 100 leads. CPA is $5,000 / 100 = $50 per lead.

Is CPA the same as CAC?

 No. CPA measures the cost of a conversion event, like a lead. CAC measures the cost of a paying customer. Many leads are needed per customer, so CAC is higher.

What counts as an acquisition in CPA?

 Whatever conversion you define: a lead, a free trial, a signup, or a sale. The definition must be consistent to compare campaigns fairly.