How to use it
Tap ACoS, Ad spend or Ad sales in the equation to pick the unknown, then fill in the other two from your Amazon Ads campaign report for the same date range. ACoS is always typed as a percentage: 25 means 25%.
Add your profit margin before ad costs to see your break-even ACoS and whether the campaign is above or below it. The margin is the share of each sale left after the product, Amazon fees and shipping. If you only know price and costs, the break-even ROAS calculator works the margin out for you.
The formula
ACoS = ad spend ÷ ad sales × 100
Ad spend = ACoS × ad sales
Ad sales = ad spend ÷ ACoS
Amazon Ads' ACOS guide gives the example: $50 spent on ads that earn $100 in sales is a 50% ACoS.
ACoS is ROAS turned upside down, so the calculator shows both:
ROAS = 1 ÷ (ACoS ÷ 100) = 100 ÷ ACoS
A 25% ACoS is 100 ÷ 25 = a 4x ROAS. If you also report to Google or Meta, the ROAS calculator works from the ROAS side.
Worked examples
Finding ACoS. A Sponsored Products campaign cost $1,200 last month and Amazon attributes $4,800 of sales to it. $1,200 ÷ $4,800 × 100 = 25.00% ACoS, a 4.00x ROAS.
Spend a target ACoS allows. You expect $6,000 of ad sales and want ACoS at 30% or lower. 30% × $6,000 = $1,800 maximum spend.
Sales an ACoS needs. You plan $900 of spend at an 18% ACoS. $900 ÷ 0.18 = $5,000 of ad sales.
| Ad spend | Ad sales | ACoS | ROAS |
|---|---|---|---|
| $1,200 | $4,800 | 25.00% | 4.00x |
| $1,800 | $6,000 | 30.00% | 3.33x |
| $900 | $5,000 | 18.00% | 5.56x |
| $50 | $100 | 50.00% | 2.00x |
ACoS and break-even ACoS
Your break-even ACoS equals your profit margin before ad costs. With a 30% margin, ads can take 30% of each ad-driven sale before that sale stops making money. Amazon Ads' guide makes the same link: ACoS has to stay below your profit margin for the ads to be profitable.
In the first example, a 25% ACoS against a 30% margin leaves 5% of ad sales as profit after ad costs. The same 25% ACoS on a product with a 20% margin loses money on every ad-driven sale. That is why this page shows no "good ACoS" figure: the line that matters is your own margin.
How this calculator handles your numbers
The sums run on exact fractions, and each result is rounded once, at the end: percentages and money to two decimals, ROAS to two decimals with an x, all half away from zero. ACoS can go above 100%, which means the ads cost more than the sales they brought in. Zero ad sales, or a zero ACoS when solving for ad sales, gets a message instead of a result, because the division has no answer.