ACoS vs ROAS on Amazon: How to Convert Them, and Which One to Use for Each Decision

Written by the BidVentor Editorial Team. Reviewed by Adeel Imrani, founder of BidVentor (14 years growing a $2M beauty brand on Amazon, $30M+ ad spend). Last updated November 2026.

Quick answer

ACoS and ROAS measure the same thing from opposite sides. ACoS is ad spend divided by ad sales, shown as a percentage. ROAS is ad sales divided by ad spend, shown as a multiple. To convert one into the other, divide 1 by it: a 25% ACoS is a 4.0 ROAS, and a 3.0 ROAS is a 33% ACoS. Neither one is “better”. Use ACoS when you compare ad cost against your margin (bids and targets), and ROAS when you talk about return on a budget (scaling, reporting, comparing channels). Whichever you use, set the target from your own break-even number, not from an industry average.

Key takeaways

• ACoS = ad spend ÷ ad sales × 100. ROAS = ad sales ÷ ad spend. They are reciprocals, so ACoS = 100 ÷ ROAS.
• Your break-even ACoS equals your margin before ad costs. Your break-even ROAS is 1 ÷ that margin.
• ACoS fits bid and keyword decisions, because it lines up directly with your margin. ROAS fits budget and channel decisions, because it reads as “what comes back per dollar”.
• Both only count attributed ad sales. Neither tells you whether the account is profitable overall, so pair them with TACoS and profit per unit.
• Pick one metric for each decision, write the target per product group, and stop switching between them mid-conversation.

The two formulas, side by side

Amazon reports both numbers in Campaign Manager, so most sellers see them every day. The maths is short:

• ACoS (advertising cost of sales) = ad spend ÷ attributed ad sales × 100
• ROAS (return on ad spend) = attributed ad sales ÷ ad spend

Take a campaign that spent $500 and drove $2,000 in attributed sales. ACoS is 500 ÷ 2,000 = 25%. ROAS is 2,000 ÷ 500 = 4.0, often written as 4x or $4 back per $1 spent.

Because one is the flip of the other, a falling ACoS always means a rising ROAS, and the reverse. There is no situation where one improves and the other gets worse. If two reports seem to disagree, they are almost always using different date ranges, attribution windows or campaign types.

ACoS to ROAS conversion table

Keep this table next to your bid sheet. ROAS = 100 ÷ ACoS, and ACoS = 100 ÷ ROAS.

ACoS	ROAS	What you keep from each $100 of ad sales, before product costs
10%	10.0	$90
15%	6.7	$85
20%	5.0	$80
25%	4.0	$75
30%	3.3	$70
33%	3.0	$67
40%	2.5	$60
50%	2.0	$50
75%	1.3	$25
100%	1.0	$0

Notice how the scale bends. Moving from 50% to 25% ACoS doubles ROAS from 2.0 to 4.0. Moving from 25% to 12.5% doubles it again to 8.0, but only saves another $12.50 per $100 of sales. That is why chasing very low ACoS on a mature product often costs you sales for a small gain.

Work out your break-even ACoS and ROAS first

A target only means something next to your margin. Here is the five-minute version.

1. Take the selling price. Say $30.
2. Subtract every cost except ads. Product cost, inbound shipping, FBA fulfilment fee, referral fee and any average returns cost. Say that totals $18.
3. Your margin before ads is $12, or 12 ÷ 30 = 40%.
4. Break-even ACoS = 40%. Above that, each ad sale loses money on that sale.
5. Break-even ROAS = 1 ÷ 0.40 = 2.5. Below 2.5, the same thing is true.

These are illustrative numbers. Use your own costs, and redo the sum when fees or prices change. Our guide to what is a good ROAS on Amazon shows how to set a target above break-even for each type of campaign.

From there, set a target for each product group, not one for the whole account. A mature hero product might aim for 25% ACoS (4.0 ROAS) to leave room for profit. A launch might accept 50% or more for a few weeks while it builds rank and reviews. A brand defence campaign on your own name often runs far below break-even, and that is fine.

Which metric to use for each decision

The practical difference between ACoS and ROAS is not the maths. It is which one makes a given decision easier to get right.

Bids and keyword targets: use ACoS

When you decide whether a keyword earns its bid, you are comparing ad cost with margin. ACoS is already in those terms: a 40% margin and a 32% ACoS tells you at a glance that there is room. It also plugs straight into the max CPC formula: max CPC = price × conversion rate × target ACoS. At $30, 10% conversion and a 30% target, you can pay up to $0.90 a click. See our guide to working out your max CPC for the full method.

Budgets and scaling: use ROAS

When you decide where the next $1,000 of budget goes, ROAS reads more naturally: campaign A returns $4.20 per dollar, campaign B returns $2.10. It also makes the scaling question clearer. Adding budget to a 6.0 ROAS campaign usually lowers its ROAS as it reaches less likely buyers, so the real question is whether the extra spend stays above your break-even ROAS.

Reporting to a team or client: pick one and stick to it

Most confusion comes from mixing the two in one meeting. Finance teams often think in ROAS. Amazon PPC managers often think in ACoS. Agree on one for the report, and add the other in brackets if needed.

Comparing Amazon with other channels: ROAS, with care

Google and Meta report ROAS, so it is the easier bridge. But attribution differs. Amazon credits sales within its attribution window (commonly 7 days for sellers’ Sponsored Products and 14 days for Sponsored Brands and Display), so a straight comparison flatters one side or the other.

Five traps that make ACoS and ROAS mislead you

1. Ignoring the attribution delay. Sales keep landing in reports for several days after a click. If you judge yesterday’s ACoS, you will cut bids on targets that are actually working. Look at periods that ended at least a week ago.

2. Judging targets on too few clicks. A keyword with 9 clicks and no orders has an infinite ACoS, but that tells you little. A useful rule of thumb is to wait for about 3 ÷ conversion rate in clicks, so 30 clicks at a 10% conversion rate, before you call a target a loser. Our post on PPC clicks but no sales explains the threshold.

3. Treating ACoS as profit. A 20% ACoS on a product with a 15% margin still loses money. A 45% ACoS on a product with a 60% margin makes money. The number only matters next to the margin. We cover this in why ACoS does not equal profit.

4. Forgetting organic sales. Ads that rank a product can lift organic sales that never show in ACoS or ROAS. TACoS (ad spend ÷ total sales) catches that effect. If ACoS is flat but TACoS is falling, ads are probably helping organic rank. See TACoS vs ACoS.

5. Blending campaign types. Branded search, competitor targeting, launch and remarketing campaigns all have different jobs. An account-wide ACoS hides a 12% branded campaign propping up a 70% competitor campaign. Split before you judge.

A worked example: one product, two readings

Here is an illustrative example, not client data. A $25 kitchen product has a 36% margin before ads, so its break-even ACoS is 36% and its break-even ROAS is about 2.8.

Last month’s search term report for its main auto campaign shows:

Search term	Spend	Ad sales	ACoS	ROAS
Term A	$210	$900	23%	4.3
Term B	$180	$400	45%	2.2
Term C	$95	$0	none	0
Campaign total	$485	$1,300	37%	2.7

At campaign level, the product looks just over break-even: 37% ACoS, or 2.7 ROAS. Cutting the campaign budget would be the obvious reaction. Looking one level down tells a different story:

• Term A is well inside the margin. Harvest it into an exact match campaign with its own bid.
• Term B is above break-even. Lower its bid toward the max CPC, or check whether the listing answers what those shoppers want.
• Term C has spent $95 with no orders. Check whether it has had enough clicks under the 3 ÷ conversion rate rule. If so, add it as a negative.

Fixing B and C, without touching the budget, would move the campaign well inside break-even. The metric was not wrong. It was measured at the wrong level.

When the problem is not the bid

If a product’s ACoS rises across many keywords at once, a bid problem is less likely than a conversion problem. Higher ACoS with steady CPC usually means fewer clicks are turning into orders: a price change, a new competitor, a lost Buy Box, fewer in-stock days, or reviews that raised a worry shoppers didn’t have before.

That is where reading your reviews helps. Before cutting bids across the board, check what recent buyers praise and complain about, then fix the listing so the shoppers you are paying for actually convert.

How BidVentor helps with ACoS and ROAS

The BidVentor PPC tool connects to your Amazon Ads account through the Amazon Ads API (BidVentor is a verified Amazon Ads partner), or works from your bulk files if your team prefers. It shows where ad money goes and whether it comes back: bids out of line with how a target converts, search terms that spend without orders, missing negative keywords, and budgets that need attention. Each recommendation comes with the metrics behind it, including ACoS, ROAS, CPC, CTR and spend, so you can check the reasoning before you act. The PPC tool carries a 4X ROAS guarantee that applies to PPC only, and terms apply.

For the conversion side, Buyer Blueprint reads all reviews for your ASIN or a competitor’s and shows why people buy and what nearly stopped them. Listing Genius COSMO turns that buyer language into a title, bullets and description built for Amazon’s COSMO algorithm and Rufus.

You get one free analysis after you sign up, which is a simple way to see where your own ACoS is coming from.

Frequently Asked Questions

Is ACoS or ROAS better for Amazon PPC?

Neither is better, because they carry the same information. ACoS is easier for bid and keyword decisions because it compares directly with your margin. ROAS is easier for budget and channel decisions because it reads as the return per dollar. Choose one per decision and set its target from your break-even number.

How do I convert ACoS to ROAS?

Divide 100 by the ACoS percentage. A 20% ACoS is a 5.0 ROAS, and a 40% ACoS is a 2.5 ROAS. To go the other way, divide 100 by the ROAS: a 3.0 ROAS is a 33% ACoS.

What is a good ACoS on Amazon?

A good ACoS is one below your break-even ACoS, which equals your margin before ad costs. For a product with a 40% margin, anything under 40% is profitable on the ad sale itself, and many sellers aim lower on mature products to leave room for profit.

Why does my ROAS look good but I am not making money?

ROAS and ACoS only compare ad spend with attributed ad sales. They ignore product costs, fees and returns. A 3.0 ROAS loses money if your margin before ads is under 33%. Check your break-even ROAS, and track profit per unit alongside it.

Should I use TACoS instead of ACoS or ROAS?

Use TACoS alongside them, not instead. ACoS and ROAS judge campaigns and keywords. TACoS, which is ad spend divided by total sales, shows whether advertising is helping the whole product, including organic sales.

Sources and further reading

• Amazon Ads guide to ACoS (advertising cost of sales).

Related guides

• What is a good ROAS on Amazon?
• TACoS vs ACoS: the hidden metric
• Why ACoS does not equal profit

About the reviewer

Adeel Imrani is the founder of BidVentor. He spent 14 years growing a $2M beauty brand on Amazon and has managed $30M+ in ad spend. Read more on his author page.

How we make this content

These guides are written by the BidVentor Editorial Team and reviewed by Adeel Imrani. Where we cite Amazon features or numbers, we link to Amazon’s own documentation. We update guides when Amazon’s tools or our guidance change, and we describe BidVentor’s features as they work today. See our methodology, or contact us with corrections.