---
title: "ACOS vs ROAS: difference and conversion | Product Metrics"
description: "ACOS is ad spend as a share of ad revenue; ROAS is ad revenue per euro spent. One is the inverse of the other, and each product breaks even at its own margin."
canonical: "https://www.productmetrics.io/glossary/acos-vs-roas"
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

# ACOS vs ROAS

ACOS is ad spend as a percentage of ad revenue, while ROAS is ad revenue divided by ad spend, so each is the inverse of the other.

## Formula

`ACOS = ad spend ÷ ad revenue × 100 · ROAS = ad revenue ÷ ad spend · ACOS = 100 ÷ ROAS`

Break-even ACOS is the margin as a percentage, and break-even ROAS is 1 ÷ margin. Use the margin left after all variable costs, not the markup.

## Example

ACOS and ROAS side by side, for a product with a 30% margin:

| ACOS | ROAS | Reading | Margin − ad spend, per €100.00 of ad revenue |
| --- | --- | --- | --- |
| 20% | 5 | Profit | €30.00 − €20.00 = €10.00 |
| 25% | 4 | Profit | €30.00 − €25.00 = €5.00 |
| 30% | 3.33 | Break-even | €30.00 − €30.00 = €0.00 |
| 33.3% | 3 | Loss | €30.00 − €33.33 = −€3.33 |
| 50% | 2 | Loss | €30.00 − €50.00 = −€20.00 |

Every €100.00 of ad revenue leaves €30.00 of margin to pay for the ads. An ACOS below 30%, or a ROAS above 3.33, earns a profit. Illustrative data.

## For one product, and for an account

Break-even moves with margin, so it moves from product to product. A product with a 50% margin can run at an ACOS of up to 50%, a ROAS of 2, before it stops earning. Set one account-wide target of 40% and the 30% product in the table loses money, while the 50% product is held back on a lead it never needed.

ACOS is the metric Amazon Ads works in, while Google Ads sets target ROAS as a percentage: a 500% target means €5.00 of conversion value per €1.00 spent, which is an ACOS of 20%. If you advertise on both, convert to one metric before comparing products.

## Common mistake

Subtracting from 100 to convert. It feels tidy and gives the wrong answer: an ACOS of 25% is a ROAS of 4 (100 ÷ 25), not 0.75 or 75%.

## Questions

### Is ACOS the inverse of ROAS?

Yes. Amazon’s ACOS guide calls ROAS the inverse of ACOS, so divide 100 by either one to get the other. A ROAS of 4 is an ACOS of 25%, and an ACOS of 20% is a ROAS of 5.

### What is break-even ACOS?

Break-even ACOS is the ACOS at which ad spend uses up all of a product’s margin, so it equals the margin as a percentage. Amazon’s guide says ACOS needs to be lower than your profit margin to keep a profit. With a 30% margin, break-even ACOS is 30% and break-even ROAS is 3.33.

### Should I use ACOS or ROAS?

They carry the same information, so use the one your ad platform reports and set the target from each product’s margin. A lower ACOS and a higher ROAS both mean less ad spend per euro of revenue.

## Sources

- [Amazon Ads: ACOS (advertising cost of sales) guide](https://advertising.amazon.com/library/guides/acos-advertising-cost-of-sales)
- [Google Ads Help: About target ROAS bidding](https://support.google.com/google-ads/answer/6268637)

## Keep reading

- [ROAS](https://www.productmetrics.io/glossary/roas): Return on ad spend, its formula and a worked example.
- [Contribution margin](https://www.productmetrics.io/glossary/contribution-margin): The margin that sets break-even ACOS and break-even ROAS.
- [Break-even ROAS calculator](https://www.productmetrics.io/break-even-roas-calculator): Find the return each product needs to break even.
- [How to calculate ROAS](https://www.productmetrics.io/blog/how-to-calculate-roas): The ROAS formula step by step, including the ACOS conversion.
- [What is a good ROAS?](https://www.productmetrics.io/blog/what-is-a-good-roas): Read your return against each product’s own break-even.
- [POAS vs ROAS](https://www.productmetrics.io/blog/poas-vs-roas): Measure profit per euro of ad spend instead of revenue.

---

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

HTML version: https://www.productmetrics.io/glossary/acos-vs-roas