How this calculator works
Cost per acquisition, also called cost per action or cost per conversion, is the ad spend needed to produce one conversion. Ad spend is clicks multiplied by the average cost per click. Dividing by the conversions attributed to those clicks gives the CPA. The conversion rate shows how many clicks became conversions and explains movements in CPA: a fall in conversion rate raises CPA even when the cost per click is unchanged.
Formula
Ad spend = clicks × average CPC. CPA = ad spend / conversions. Conversion rate = conversions / clicks × 100.
Worked example
2,000 clicks at $1.50 each cost $3,000. With 40 conversions the CPA is $75 and the conversion rate is 40 / 2,000 = 2%.
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Frequently asked questions
How is CPA different from CAC?
CPA usually measures a single tracked action, such as a lead form or a purchase attributed to an ad campaign. Customer acquisition cost looks at the whole business and includes all marketing and sales spending spread over new customers won.
Should I use clicks or impressions?
If you pay per click, spend is clicks times CPC. If you pay per thousand impressions, use the CPM and CPC calculator to convert the CPM to an effective CPC first, then use this page.
Why is CPA missing when there are no conversions?
The input requires at least one conversion because dividing spend by zero conversions gives no finite answer. A campaign with no conversions has no measurable CPA yet.