To convert ACoS to ROAS, divide 100 by the ACoS percentage: ROAS = 100 ÷ ACoS%. A 25% ACoS is a ROAS of 4, a 50% ACoS is a ROAS of 2. To go the other way, ACoS% = 100 ÷ ROAS, so a ROAS of 5 is a 20% ACoS. The two numbers measure the same thing, ad spend against ad sales, turned upside down.
Amazon reports ACoS (advertising cost of sales) in its ad console, while Google, Meta and most ecommerce tools report ROAS (return on ad spend). If you sell on Amazon and somewhere else, you'll keep switching between them. This guide gives the formulas, a conversion table, worked examples and the break-even point for each. The free ROAS calculator shows ROAS and ACoS side by side from your ad spend and sales.
- ACoS = ad spend ÷ ad sales × 100.
- ROAS = ad sales ÷ ad spend.
- ACoS to ROAS: ROAS = 100 ÷ ACoS%. 30% ACoS = 3.33 ROAS.
- ROAS to ACoS: ACoS% = 100 ÷ ROAS. ROAS 4 = 25% ACoS.
- Lower ACoS is better; higher ROAS is better. Break-even ACoS equals your margin before ads.
What are ACoS and ROAS?
Both compare what you spent on ads with the sales those ads brought in. Amazon Ads defines ACoS as ad spend divided by ad revenue, times 100, and describes ROAS as its inverse: ad revenue divided by ad spend.
| ACoS | ROAS | |
|---|---|---|
| Stands for | Advertising cost of sales | Return on ad spend |
| Formula | Ad spend ÷ ad sales × 100 | Ad sales ÷ ad spend |
| Written as | A percentage (25%) | A ratio or multiple (4 or 4:1) |
| Better when | Lower | Higher |
| Mostly used by | Amazon Ads | Google Ads, Meta, Shopify and most other tools |
Example: $200 of ad spend that brings $800 of ad-attributed sales is a 25% ACoS ($200 ÷ $800) and a ROAS of 4 ($800 ÷ $200).
How do you convert ACoS to ROAS?
Divide 100 by the ACoS percentage. If you write ACoS as a decimal (0.25 instead of 25%), divide 1 by it instead.
- Take your ACoS from the Amazon ad console, for example 32%.
- Divide 100 by it: 100 ÷ 32 = 3.125.
- That's your ROAS: every $1 of ads brought about $3.13 in ad sales.
- To check, multiply them: ACoS% × ROAS should equal 100 (32 × 3.125 = 100).
ACoS to ROAS conversion table
| ACoS | ROAS | Ad sales per $1 of ads |
|---|---|---|
| 10% | 10.00 | $10.00 |
| 15% | 6.67 | $6.67 |
| 20% | 5.00 | $5.00 |
| 25% | 4.00 | $4.00 |
| 30% | 3.33 | $3.33 |
| 35% | 2.86 | $2.86 |
| 40% | 2.50 | $2.50 |
| 50% | 2.00 | $2.00 |
| 60% | 1.67 | $1.67 |
| 75% | 1.33 | $1.33 |
| 100% | 1.00 | $1.00 |
The relationship isn't a straight line. Cutting ACoS from 50% to 40% lifts ROAS by 0.5, but cutting it from 20% to 10% lifts ROAS by 5. Small ACoS changes matter much more at the low end.
How do you convert ROAS to ACoS?
Divide 100 by the ROAS. A ROAS of 2.5 is 100 ÷ 2.5 = 40% ACoS; a ROAS of 8 is 12.5% ACoS. This is useful when a target is set in ROAS (for example a Google Ads target ROAS) and you want to apply the same goal to Amazon campaigns.
| ROAS | ACoS |
|---|---|
| 1.5 | 66.7% |
| 2 | 50% |
| 3 | 33.3% |
| 4 | 25% |
| 5 | 20% |
| 6 | 16.7% |
| 8 | 12.5% |
| 10 | 10% |
What ACoS and ROAS do you need to break even?
Break-even ACoS equals your profit margin before ad costs. Break-even ROAS is 1 ÷ that margin. If a product keeps 30% of its price after product cost, Amazon fees and shipping, ads break even at a 30% ACoS, which is a 3.33 ROAS. Below 30% ACoS (above 3.33 ROAS) the ads add profit; above it, each ad sale loses money.
| Margin before ads | Break-even ACoS | Break-even ROAS |
|---|---|---|
| 20% | 20% | 5.00 |
| 30% | 30% | 3.33 |
| 40% | 40% | 2.50 |
| 50% | 50% | 2.00 |
Work out the margin first with the free profit margin calculator, then read break-even ROAS for the full method with fees, shipping and returns.
A $30 product costs $9 to make, Amazon referral and fulfilment fees take $10, and $2 goes on other per-order costs. That leaves $9, a 30% margin before ads. Last month $450 of ads brought $1,800 of ad sales: ACoS 25%, ROAS 4. Both beat break-even (30% and 3.33), so the ads made money: $1,800 × 30% = $540 of margin, minus $450 of ads, is $90 of profit.
What is TACoS, and how is it different?
TACoS (total advertising cost of sales) divides ad spend by all your sales, not just the ones ads were credited with. It's a common seller metric rather than a column in every Amazon report, so you usually work it out yourself: $450 of ads against $4,500 of total sales is a 10% TACoS. ACoS tells you whether the ads pay for themselves; TACoS tells you how much of the business depends on them. If TACoS falls while sales grow, organic sales are growing too.
Why do ACoS and ROAS sometimes not match across platforms?
- Attribution windows differ. Each ad platform credits sales over its own window after a click or view, so the same campaign can report different sales in different tools.
- Some reports use different sales figures. Check whether a report uses sales before or after discounts, tax and refunds.
- Date ranges and time zones. Compare ad spend and sales for exactly the same period.
- Tracking links. For traffic you send to your own store, tag links with UTM parameters so sales are credited to the right source.
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Make a video ad7 days free · 50 credits · No credit cardWhich should you track, ACoS or ROAS?
Use whichever your ad platform reports, and convert when you compare. Many sellers track ACoS inside Amazon because the console shows it, and ROAS everywhere else. What matters more than the metric is the line you compare it with: your break-even, and the target that leaves the profit you want. See how to calculate ROAS and what is a good ROAS, and if you sell on Amazon, AI tools for Amazon sellers. More on pricing, margins and ads in our selling online guides.
Frequently asked questions
How do I convert ACoS to ROAS?
Divide 100 by the ACoS percentage. A 20% ACoS is 100 ÷ 20 = a ROAS of 5.
What ROAS is a 30% ACoS?
3.33. Every $1 of ads brought about $3.33 in ad sales.
Is a lower ACoS always better?
Not always. A very low ACoS can mean you're bidding too little and missing profitable sales. Aim for an ACoS below your margin before ads, at a level that still grows sales.
What is a good ACoS on Amazon?
One below your break-even ACoS, which equals your profit margin before ads. A product with a 40% margin is profitable on ads at any ACoS under 40%.
Is ROAS the same as ROI?
No. ROAS compares ad sales with ad spend. ROI compares profit with the total cost, so it accounts for product cost and fees as well.
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