Cost per Acquisition is the total ad spend on a campaign divided by the number of conversions it produced. 'Conversion' can mean a purchase, a signed-up trial, a qualified lead — whatever you've defined as the meaningful action.
CPA = Ad Spend / Conversions
Why it matters
CPA is the operational counterpart of ROAS. ROAS tells you efficiency in revenue terms; CPA tells you what it costs you to fill the top of the funnel. A target CPA falls out of unit economics: if your average order value is €80 and your contribution margin after fulfilment is 35%, you have €28 to spend per acquired customer to break even on the first order. Anything below is profitable on the first transaction; anything above relies on repeat purchases.
CPA vs CAC
These are often used interchangeably but they're not the same. CPA covers paid-acquisition spend only. Customer Acquisition Cost (CAC) divides by the number of customers but adds in everything that helped acquire them — content production, agency fees, software, the percentage of marketing salary attributable to that channel. CAC is always higher.
Typical ranges
- DTC ecommerce: €15 – €60 for a first purchase, depending on AOV and category competitiveness
- B2B SaaS trial-to-paid: €100 – €500 per paying customer is common; bigger contract values support higher CPAs
- Lead-gen for high-ticket services: €30 – €200 per qualified form fill
- If your CPA is rising 30%+ month-over-month with the same creative, the audience is fatiguing — refresh the hook before you raise budgets