About this tool
The CPA Calculator divides what a campaign cost by the conversions it produced to give cost per acquisition, and it runs the same formula backward: enter a CPA and a conversion goal to see the spend it implies, or a CPA and a budget to see how many conversions that budget should buy. It is for performance marketers reading platform reports, for owners deciding whether a channel pays for itself, and for anyone who needs a defensible target CPA rather than a guess. The target panel builds that ceiling from average order value, gross margin, and the share of margin you are willing to spend winning an order, then grades your actual CPA against it. A conversion-rate table shows how far CPA moves when the same clicks convert at different rates.
How it works
CPA = spend ÷ conversions. Solving for spend gives spend = CPA × conversions, and solving for conversions gives conversions = spend ÷ CPA. Target CPA = average order value × gross margin × acquisition share; with a 100% share every unit of gross profit goes to advertising, which is the break-even CPA = order value × gross margin. When clicks are supplied the page derives CPC = spend ÷ clicks and conversion rate = conversions ÷ clicks, and uses the identity CPA = CPC ÷ conversion rate to tabulate CPA at other conversion rates. The currency symbol is display only; no exchange rates are applied.
Frequently asked questions
What counts as a conversion for CPA?
Whatever action the campaign is optimized for: a purchase, a lead form, a trial sign-up, an app install, or a phone call. CPA is only comparable across campaigns when they count the same action, so a lead-generation CPA of 15 and an e-commerce purchase CPA of 40 are not better or worse than each other; they price different things.
How do I set a target CPA?
Start from what a conversion is worth. For a sale, multiply average order value by gross margin to get the gross profit per order; that is the most you could pay before losing money. Then decide what share of that profit you will spend on acquisition. At a 120 order value, 50% margin, and a 70% share, the target CPA is 42 and anything under it leaves at least 18 of profit per order.
What is the difference between CPA and CAC?
CPA prices any conversion, including repeat purchases, leads, and sign-ups that never pay. CAC, customer acquisition cost, divides all sales and marketing cost by new paying customers only. CPA is a campaign metric read from an ad platform; CAC is a business metric that usually comes out higher because it includes salaries, tools, and unconverted leads.
Why does my CPA change when nothing else did?
CPA is CPC divided by conversion rate, so it moves whenever either input moves. A seasonal dip in conversion rate from 2.5% to 2% raises CPA by 25% at the same cost per click, and auction competition can push CPC up with no change on your site. The conversion-rate table on this page shows exactly how sensitive your CPA is.