CPC vs CPA
CPC = spend ÷ clicks and CPA = spend ÷ conversions. CPC tells you how efficiently you buy attention; CPA tells you what each customer actually costs. CPA is the one tied to profit — pair it with the break-even ROAS calculator to know the ceiling it must stay under.
Improving the funnel
Since CPA = CPC ÷ conversion rate, work both levers: cheaper, more relevant clicks and a higher-converting page. Track your conversion rate and CPM alongside CPA to see where the leak is.
Frequently asked questions
How do you calculate CPC and CPA?
CPC (cost per click) = ad spend ÷ clicks. CPA (cost per acquisition) = ad spend ÷ conversions. So $500 over 1,200 clicks is a $0.42 CPC, and if those clicks produced 36 sales, your CPA is about $13.89. CPA is the number that actually maps to profit, since clicks only matter if they convert.
What's a good CPA?
A good CPA is any CPA below your break-even cost per acquisition, which depends on your margins. If you make $40 profit on a sale, a $20 CPA is healthy; if you make $15, that same $20 CPA loses money. Always judge CPA against your unit economics, not a generic benchmark.
How can I lower my CPA?
Lower CPC (better creative and targeting) and raise conversion rate (faster, clearer landing pages and a stronger offer). Because CPA = CPC ÷ conversion rate, improving either one pulls CPA down. The biggest lever is usually creative: a proven ad angle lowers CPC and lifts conversions at the same time.
How does CPA relate to ROAS?
They measure the same thing from different sides. CPA is what you pay per sale; ROAS is the revenue you get per dollar spent. If your average order value is fixed, a lower CPA means a higher ROAS. Use the ROAS calculator alongside this to see the full picture.