How to use the CPA calculator
CPA is the ad cost of winning one conversion: ad spend ÷ conversions. A conversion is whatever action you decided to count, such as a purchase, a signup or a booked call, so define it before comparing periods.
Add average revenue per conversion and the tool returns ROAS (revenue per conversion ÷ CPA) along with revenue per conversion minus CPA. A negative figure there means each sale cost more in advertising than it brought in.
Add your contribution margin and the tool also shows profit per conversion, subtracting CPA from what is left after variable costs. With a thin margin, profit can be negative even when revenue exceeds CPA, so use the sign of that row when deciding whether to scale a channel.
CPA also breaks down into CPC ÷ conversion rate, which is useful when CPA runs above target: you can push on the click price or on the landing page rate. Keep ad spend and conversions on the same period and the same campaigns.
Frequently asked questions
CPA equals CPC divided by conversion rate. Cheap clicks with a weak rate still produce an expensive CPA, while pricey clicks with a strong rate can keep CPA low.
There is no general benchmark because it depends entirely on your order value and margin. Enter revenue per conversion and your margin and check whether profit per conversion stays positive.