What Is a Good Amazon ACOS? Start With Your Margins

A lower ACOS can look reassuring, but it is not a complete profit calculation. Start with what a sale contributes to your business before choosing an advertising target.

What ACOS and ROAS measure

ACOS is advertising spend divided by ad-attributed sales, expressed as a percentage. ROAS reverses that comparison: attributed sales divided by spend. Neither metric deducts product costs or selling fees.

Calculate the room available for ads

Suppose a product sells for $40 and leaves $12 after the product cost, marketplace fees, fulfilment and other variable costs, but before advertising. That gives it a 30% pre-ad contribution margin. In this simplified example, spending $12 on ads for that sale consumes the whole contribution.

At 20% ACOS, the advertising cost allocated to a $40 sale would be $8, leaving $4 before any costs excluded from the calculation. This is an illustration with assumed inputs, not a forecast. Discounts, returns, taxes, management fees and overheads may change the full picture.

Choose a target for the objective

Amazon does not prescribe one universally good ACOS. A campaign intended to protect contribution needs a different evaluation from a deliberately funded discovery test. Define that purpose and its spending boundary in advance rather than explaining an overrun afterwards.

Read performance in context

Compare like with like: the same product economics, campaign purpose and reporting basis. Do not treat attributed revenue as proof that every sale was caused by the ad. Review total commercial performance alongside the campaign report.

Before setting your target

• List the costs included in your margin calculation.
• Separate attributed revenue from profit.
• Define the campaign objective and acceptable spending.
• Record when you will revisit the target.

Discuss a more focused approach to PPC management.

Further reading

Amazon Ads: ACOS calculations, margins and campaign goals. Guidance checked on 28 October 2026.