Free marketing calculator · Acquisition efficiency
Cost Per Acquisition (CPA) Calculator
Calculate the average advertising cost of each conversion or acquisition, then use the result alongside conversion rate, CAC and ROAS.
CPA is simple to calculate but easy to misuse. The number only becomes meaningful when the conversion event is defined consistently and represents something commercially useful.
What is CPA?
Cost per acquisition (CPA) is the average advertising spend required to generate one chosen conversion or acquisition. Depending on the campaign, that event might be an order, a paid sign-up, a booked consultation or another completed action.
Example: £8,000 of advertising spend generating 400 conversions gives a CPA of £20.
CPA is only as useful as the conversion you count
A purchase and a newsletter sign-up are both technically conversions, but they carry very different commercial value. Before comparing CPA between campaigns, make sure the conversion definition, attribution window and measurement period are comparable.
For ecommerce, CPA often refers to the media cost per order. In lead generation, it may refer to a qualified enquiry or booked appointment. If you mean the total cost of acquiring an actual customer across marketing and sales, customer acquisition cost (CAC) is usually the more appropriate metric.
How CPA connects to CPC and conversion rate
CPA can rise because clicks became more expensive, because fewer clicks converted, or because both changed at once. That is why CPA should be diagnosed alongside CPC and conversion rate.
If CPC is £1 and 5% of clicks convert, the implied CPA is £20. Use the conversion rate as a decimal in the arithmetic: £1 ÷ 0.05 = £20.
Is a lower CPA always better?
No. A lower CPA is valuable only if the acquisitions are valuable. A campaign can reduce CPA by attracting easier-to-convert users while simultaneously reducing average order value, repeat purchase behaviour or margin. Read CPA together with revenue, contribution and customer value.
See the whole campaign funnel
The Campaign Performance Calculator connects CPA with impressions, clicks, CTR, CPC, CPM, leads, conversion rates, revenue, ROAS and contribution.
CPA calculator FAQs
What is a good CPA?
There is no universal good CPA. The sustainable level depends on the value and margin generated by the acquisition, repeat purchase behaviour, attribution and the costs excluded from the media-only calculation.
What is the difference between CPA and CAC?
CPA normally measures advertising spend per selected conversion. CAC is broader and usually measures the total acquisition cost required to gain a new customer, often including more than media spend alone.
Can CPA be calculated with zero conversions?
No meaningful finite CPA exists when there are no conversions. The calculator should therefore treat a zero conversion denominator as unavailable rather than reporting a misleading number.