SellerUtils

CPA Calculator

Actual cost per order shows how much advertising you spent for each attributed purchase. CPA = ad spend ÷ attributed orders. Add new-customer counts to compare ad-only CAC and a target ROAS to examine an allowable CPA.

Your campaign performance

$

Same period and attribution basis; weighted conversions may be fractional.

$

After refunds, excluding sales tax.

A subset of these orders, for an ad-only CAC comparison.

%

After variable selling costs, before advertising.

Enter a ratio such as 3, not 300%.

Results

Actual cost per order (CPA)

$20.00

Advertising spend divided by attributed orders. Repeat purchases may be included.
ROAS
2.5
Average order value
$50.00
CPA limit for target ROAS
$16.67
Break-even CPA under your margin
$20.00
Total contribution after ads
$0.00
Ad-only CAC excludes non-ad acquisition costs. Orders, revenue and new customers must use consistent attribution.

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CPA uses attributed orders; optional CAC uses new customers and advertising spend only. Contribution estimates are before fixed overhead and taxes. Read the formulas and assumptions.

How to calculate actual CPA

  1. Use advertising spend, order conversions and attributed revenue from the same reporting period and attribution window.
  2. Enter new customers only if you can identify them within those orders. Leave the field blank otherwise.
  3. Enter your contribution margin before ads if you want to assess the economics.
  4. Enter a target ROAS as a ratio, such as 3, to calculate the implied CPA limit. A target is a planning assumption, not measured performance.

Campaign formulas

  • Actual CPA = Ad spend ÷ Orders
  • Ad-only CAC = Ad spend ÷ New customers
  • Average order value = Attributed revenue ÷ Orders
  • ROAS = Attributed revenue ÷ Ad spend
  • Target CPA = Average order value ÷ Target ROAS
  • Contribution after ads = Revenue × Pre-ad margin − Ad spend

Worked example: orders versus customers

A campaign spends $1,000 and records 50 orders with $2,500 revenue. CPA is $20, average order value is $50 and ROAS is 2.5. If 25 of the orders are first purchases by distinct new customers, ad-only CAC is $40.

At a 40% contribution margin, the orders contribute $1,000 before ads and $0 after ads. A target ROAS of 3 allows a CPA of $50 ÷ 3 ≈ $16.67. Actual CPA is above that target but exactly at the first-order break-even limit of $20.

Avoid mixing attribution and profitability

Attribution systems can credit the same order to multiple campaigns or platforms. A low reported CPA does not prove that the ads generated incremental customers. Fractional orders can represent attribution weighting; customer counts must use a compatible basis.

For a detailed per-order cost model, use break-even CPA. For repeat-customer economics, use customer lifetime value. Keep fully loaded acquisition costs separate from this ad-only comparison.

Cost-per-conversion context

Google Ads' ROI guide connects conversion costs with revenue and profitability. This page defines the conversion specifically as an order. Source checked October 8, 2026.

Frequently asked questions

What does CPA mean in this calculator?

It means advertising cost per attributed order: ad spend divided by attributed orders. CPA can mean other conversion actions elsewhere; this tool specifically uses completed orders.

How is CPA different from CAC?

Orders can include repeat purchases. CAC uses new customers as its denominator. The optional CAC here divides only advertising spend by new customers, so it excludes other acquisition costs.

How is this different from break-even CPA?

Actual CPA uses measured campaign spend and orders. Break-even CPA is the spending limit your order contribution can support. Compare actual CPA with that limit rather than treating them as interchangeable.

What happens with zero orders or zero spend?

With zero orders, cost per order is undefined; spending remains a cost. With positive orders and zero spend, CPA is zero and ROAS is undefined. The tool explains these cases without displaying Infinity.

Is hitting my target ROAS enough to be profitable?

Only if the target is high enough for your margin. Target CPA = average order value ÷ target ROAS. If that limit exceeds order contribution before ads, the target can still allow a loss.

By the SellerUtils team · Last updated October 8, 2026. Results are estimates for planning and are not financial advice.

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