---
title: "CAC vs CPA: the difference, with example | Product Metrics"
description: "CPA divides ad spend by every conversion, CAC by new customers only. Same spend, two answers: a worked month, and which question each metric settles."
canonical: "https://www.productmetrics.io/glossary/cac-vs-cpa"
pageType: article
language: en
publisher: "Product Metrics"
author: "Berend Vrakking"
datePublished: 2026-10-07
dateModified: 2026-10-07
---

> Content index: https://www.productmetrics.io/llms.txt

# CAC vs CPA

CPA divides ad spend by every conversion, while CAC divides it by new customers only, so CPA looks cheaper whenever returning customers buy too.

## Formula

`CPA = ad spend ÷ conversions · CAC = ad spend ÷ new customers`

Same spend, a different count. New customers are part of the conversions, so with one order per customer CAC is never lower than CPA. New customer acquisition cost (nCAC) is CAC held strictly to customers who have not bought before.

## Example

One month, 100 orders, 60 from new customers:

| Step | Value |
| --- | --- |
| Ad spend | €5,000.00 |
| Conversions (orders) | 100 |
| New customers among those orders | 60 |
| CPA (€5,000.00 ÷ 100) | €50.00 |
| CAC (€5,000.00 ÷ 60) | €83.33 |

One invoice, two prices: €50.00 per order, €83.33 per new customer. The 40 returning customers are doing CPA a €33.33 favour. Illustrative data.

## For one product, and for an account

Products differ in who buys them. A product your regulars keep reordering has a low CPA and a high CAC; a product that pulls in strangers can show a higher CPA and a lower CAC. Blend them into one account CPA and you can no longer see which products win new customers.

Use CPA to judge a sale against the profit it earns. Use CAC when the question is growth, and set it against first-order profit and repeat purchases. With Full Signal Tracking, new customers get their own conversion action in Google Ads, and Product Metrics shows nCAC per product and as an account average.

## Common mistake

Putting CPA in the monthly report as the cost of a new customer. Your regulars are in that count, so winning a stranger costs more than the report says.

## Questions

### Is CAC the same as CPA?

No. Both start from the same ad spend, but CAC ignores orders from people who have bought before. The two only match in a period where every conversion came from a new customer.

### Why is my CAC higher than my CPA?

Because returning customers count towards CPA and not towards CAC. The more of your orders come from regulars, the wider the gap: in the example above, 40 repeat orders out of 100 open a gap of €33.33.

### What is the difference between CAC and ROAS?

CAC is the cost of one new customer. ROAS is the revenue each euro of ad spend brought back, from new and returning customers alike. A strong ROAS can rest on returning customers while new customers stay expensive.

## Keep reading

- [Customer acquisition cost (CAC)](https://www.productmetrics.io/glossary/cac): The formula and what a new customer has to pay back.
- [Cost per acquisition (CPA)](https://www.productmetrics.io/glossary/cost-per-acquisition): Cost per conversion, counting every sale.
- [Repeat purchase rate](https://www.productmetrics.io/glossary/repeat-purchase-rate): How many customers come back, which sets the gap between CPA and CAC.
- [Customer acquisition cost for ecommerce](https://www.productmetrics.io/blog/customer-acquisition-cost-formula): The formula, nCAC and what you can pay for a new customer.
- [LTV:CAC ratio for ecommerce](https://www.productmetrics.io/blog/ltv-cac-ratio-ecommerce): Compare what a customer brings with what they cost.
- [Full Signal Tracking](https://www.productmetrics.io/server-side-tracking): New-customer and profit conversions sent to Google Ads.

---

Written by Berend Vrakking, founder of Product Metrics. Last updated 2026-10-07.

HTML version: https://www.productmetrics.io/glossary/cac-vs-cpa