Free tool · Amazon advertising
ROAS calculator
A ROAS of 3 sounds good until you know your break-even is 3.5. Put your ads next to your margin and see whether they make money, and what ROAS you need to hit your profit target.
- Break-even ROAS
- Target ROAS
- No sign-up
Reading your figures…
- Profit from these ad sales, after ad spend
- –
- Your ROAS
- –
- Your ACoS
- –
- Break-even ROAS
- –
- Break-even ACoS
- –
- Target ROAS
- –
- Target ACoS
- –
- TACoS: ad spend as a share of all sales
- –
Counts only the sales Amazon attributes to your ads. Ads also lift organic sales, and some attributed sales would have happened anyway, so treat the profit figure as a floor for a growing product and a ceiling for a well-known one.
Below break-even on some campaigns?
Most accounts are, somewhere. In a Profit Audit we find which campaigns lose money, which ones are buying growth on purpose, and which to change first.
How it works
From ROAS to profit in three formulas
ROAS on its own tells you how much your ads sell, not whether they make money. To answer the second question you need one more number: how much of each pound of sales you keep before advertising. The calculator puts the two together.
ROAS and ACoS
ROAS = ad sales ÷ ad spend ACoS = ad spend ÷ ad sales = 1 ÷ ROAS
Two views of the same ratio. Amazon reports both in the Ads console.
Break-even ROAS
Break-even ROAS = 1 ÷ (profit before advertising ÷ (price ÷ (1 + VAT rate)))
Amazon Ads reports attributed sales without VAT (Amazon Ads help, updated 27 August 2026), so the margin is taken on the price without VAT.
Target ROAS
Target ROAS = 1 ÷ (margin before advertising − profit you want)
The ROAS that leaves the share of ad sales you want to keep as profit.
A worked example
The example loaded above is the insulated water bottle from our FBA calculator: £24.99 including VAT, which leaves £8.07 a unit before advertising. Without VAT the price is £20.83, so the margin before advertising is 38.8%. That is the break-even ACoS, and the break-even ROAS is 1 ÷ 0.388 = 2.58.
Over a month, the bottle’s campaigns spend £3,000 and Amazon attributes £9,000 of sales to them: a ROAS of 3.0 and an ACoS of 33.3%. The ads are profitable, just: £9,000 × 38.8% = £3,488 of margin, less £3,000 of spend, leaves £488. If you want to keep 10% of ad sales as profit, the target ACoS is 28.8% and the target ROAS is 3.48, so these campaigns are profitable but below target.
What the numbers leave out
Amazon credits a sale to an ad when a shopper clicked it within the attribution window, so some of those sales would have happened anyway, and some organic sales happen only because ads lifted your rank. For a new or growing product, the true return is often better than the attributed one; for a brand people already search for by name, it is often worse. That is why we read ROAS next to TACoS, and why the calculator asks for total sales.
For the full method, including how to set break-even ACoS for each product, read our guide to break-even ACoS.
Questions
About this tool.
What is ROAS on Amazon?
ROAS (return on ad spend) is the sales your ads bring in for each £1 you spend: attributed ad sales divided by ad spend. Spend £1,000 and get £4,000 of attributed sales and your ROAS is 4. It is the inverse of ACoS (advertising cost of sales), so a ROAS of 4 is the same as an ACoS of 25%.
What is a good ROAS on Amazon?
One above your break-even ROAS, which is 1 divided by your margin before advertising. A product that keeps 40% of its price (without VAT) before ads breaks even at a ROAS of 2.5; one that keeps 20% needs a ROAS of 5. That is why no single ROAS is good for everyone, and why the calculator asks for your profit per unit first.
How do I calculate break-even ROAS?
Divide 1 by your margin before advertising, measured on the price without VAT, because Amazon Ads reports attributed sales without VAT. A £24.99 product with 20% VAT sells for £20.83 before VAT; if it leaves £8.07 before advertising, the margin is 38.8% and the break-even ROAS is 2.58.
Should I use ROAS or ACoS?
They carry the same information, so use the one your team reads more easily. Amazon’s console shows both. ACoS is easier to compare with your margin (break-even ACoS equals your margin before ads); ROAS is easier to explain to a finance team (pounds back per pound spent). Whichever you use, add TACoS, which divides ad spend by all sales and shows what advertising costs the whole business.
Why does my ROAS look fine when I am losing money?
Usually because your margin before advertising is thinner than you think, or because VAT was left in. A ROAS of 3 is profitable on a 40% margin and loses money on a 30% margin. If you are VAT-registered, one sixth of a 20% VAT price never reaches you, so comparing Amazon’s ex-VAT ad sales with a VAT-inclusive margin overstates profit.
The Profit Audit
Want a senior team to read your numbers with you?
One call with Robert Prime and the team. We go through your accounts product by product and show you the changes most likely to add net profit.