CPA equals total media cost divided by conversions. $10,000 of spend producing 250 purchases is a $40 CPA. CPA can also be derived as CPC divided by conversion rate: a $2 click at a 5 percent conversion rate is a $40 CPA.
What moves it
Define the conversion and the attribution window before calculating, and separate media cost from fees unless you are reporting fully loaded CPA. Marginal CPA, the cost of the next conversion at higher spend, is higher than the average and is the figure that should govern budget changes.
Run your own numbers with the CPA and ROAS calculator.
Cite this page:
Agency Echelon. "How do you calculate CPA?" Agency Echelon Reference, reviewed September 2026. https://agencyechelon.com/reference/questions/how-to-calculate-cpa/