Free calculator

CPA calculator

Enter spend and conversion count to see cost per acquisition — then judge it against contribution margin and target POAS.

How CPA is calculated

CPA = ad spend ÷ conversions (purchases or other chosen conversion action). It answers how much you paid, on average, for each conversion in the window.

A “good” CPA is below the contribution profit you keep after COGS, shipping, and payment fees — otherwise volume grows losses.

CPA = spend ÷ conversions
Target CPA ≤ contribution profit per order (with buffer).
Pair with POAS when margins differ across SKUs.

CPA vs ROAS

CPA focuses on cost per order; ROAS focuses on revenue multiple. High AOV can support a higher CPA at the same ROAS. Use both, then validate with profit.

Frequently asked questions

What is CPA?

Cost Per Acquisition (or cost per conversion) is ad spend divided by the number of conversions. It shows how expensive each acquisition was in that period.

How do you calculate CPA?

Divide total ad spend by conversions. Example: $4,000 spend and 80 purchases → CPA = $50.

What is a good CPA?

A good CPA stays below the contribution margin (or first-order profit) you keep after product costs — often with a buffer for refunds and overhead. There is no universal industry CPA that fits every margin profile.