Cost Per Acquisition (CPA): How to Calculate It
Cost per acquisition (CPA) is the average advertising or marketing cost required to generate one defined conversion. The basic calculation is:
An acquisition might be a purchase, qualified lead, signup, or another action. Define the conversion before calculating CPA so the numerator and denominator describe the same campaign outcome.
Worked example
If a campaign spends $4,000 and produces 80 purchases:
The campaign spent an average of $50 per purchase. A campaign with no acquisitions has no finite CPA; do not report that case as zero.
What to include in spend
Use a consistent scope. Media spend alone produces a media CPA. Adding creative, agency, platform, software, or sales costs produces a broader blended CPA. Neither is automatically correct; the useful choice depends on the decision you are making.
CPA and profitability
Compare CPA with the value of the acquisition, not with a competitor's headline number. A $50 CPA may be acceptable for a customer with high contribution margin and poor for a low-margin sale. Include refunds, discounts, repeat-purchase assumptions, and attribution rules when they materially affect the decision.
For a direct numeric comparison across campaign inputs, use the CPA Calculator when available in the tool collection. For return-on-investment analysis, use the ROI Calculator.
Questions
Is CPA the same as CAC?
They can overlap, but customer acquisition cost often includes broader sales and marketing costs, while CPA may refer to one campaign or conversion event. State the scope explicitly.
What is a good CPA?
There is no universal target. A useful CPA is one that fits the margin, retention, payback period, and growth objective of the specific business.
Should I use clicks or conversions in the denominator?
Use conversions for CPA. Click cost is a different metric, usually called CPC. Mixing clicks and conversions produces a misleading result.
Scope and limitations
The embedded calculator supports simple and detailed CPA estimates. Review attribution scope, included costs, and conversion definitions before using the output for decisions.