CPA Calculator
Cost per acquisition in any direction, with the counting model explicit, and the number that actually matters derived from your margin: the CPA you can afford, and the max CPC it implies.
CPA solver enter any two, the third is solved
Full funnel
Unit economics: contribution and break-even bids
Scenario planner arithmetic from your assumptions, not a forecast
Show the math
The affordable CPA is a business number, not an ad number
Ad platforms will happily optimize toward whatever CPA target you type in; whether that target loses money is your problem. The affordable ceiling comes from order economics: what an average order contributes after product and per-order costs. This page derives break-even CPA from those inputs, connects it to a max CPC through your acquisition rate, and keeps the ROAS view beside it with break-even ROAS from the same margin. One set of economics, every bidding ceiling, consistently.
CPA FAQ
How is CPA calculated?
CPA = ad spend / conversions. $900 producing 38 acquisitions is a $23.68 CPA. The solver above runs all three directions: conversions a budget must produce to hit a target CPA, or the spend a conversion goal allows. The counting model matters: this page distinguishes unique acquisitions (real customers or leads) from all conversion actions, because platforms can count several actions per click.
What CPA can I afford?
Break-even CPA = average order value x contribution margin - fixed per-order costs. A $100 order at a 40% margin with $5 of per-order fixed costs affords a $35 CPA at break-even; pay more and each acquisition loses money on first-order economics. Enter those three numbers in the unit economics panel and the calculator derives it, plus the max CPC your acquisition rate implies.
How do CPA and max CPC connect?
Through the acquisition rate: max CPC = affordable CPA x acquisition rate. If you can pay $35 per acquisition and 4% of clicks acquire, each click is worth at most $1.40. The calculator computes this from your funnel’s actual rate when it is valid, with the caveat printed: auctions vary actual CPCs and rates drift, so treat it as a ceiling, not a bid.
Should I judge campaigns on CPA or ROAS?
They fail differently. CPA ignores order value: a $30 CPA is great for $200 orders and ruinous for $40 ones. ROAS ignores costs: a 3x ROAS loses money below a 33% margin. The pair, anchored to your contribution margin (break-even ROAS = 1/margin), covers both failure modes; this page computes all of it from one set of inputs.
More free tools: Ad Metrics Calculator · CPM Calculator · ROAS Calculator · Break-Even Calculator