Amazon advertising
Break-even ACOS calculator.
Enter the price and your per-unit costs. Break-even ACOS equals your margin before ad spend.
Break-even ACOS = margin before ad spend. A $30 item with $16.50 of cost, fees and shipping leaves $13.50, a 45% margin, so ads break even at an ACOS of 45%.
Your numbers
Result
Worked example
Price $30, product cost $9, fees $4.50, shipping $3: contribution is $13.50, margin 45%. Break-even ACOS is 45% (break-even ROAS 2.22). With a 10% profit target, target ACOS is 35%, and the most you can spend on ads per order is $10.50.
How it works
Margin = (price - per-unit costs) / price. Per-unit costs are what you enter: product cost, the marketplace fees and fulfillment you pay on each unit, and anything else that scales with a sale. This tool has no fee tables, so use your own current numbers from your seller account.
Break-even ACOS = margin. Ads break even when ad spend equals the profit on the ad-attributed sales, which is ACOS = margin. Amazon Ads says the same in plain words: break-even ACOS is directly linked to your profit margin, and ACOS must stay below it to be profitable.
Target ACOS = margin - target profit. Break-even ROAS = 1 / margin.
Fixed costs such as software and staff, returns and storage that are not in your per-unit costs are not included. Repeat purchases are not included either.
Source (opened 2026-10-18): What is advertising cost of sales (ACOS)? Calculation and tips - Amazon Ads. Everything else is arithmetic on your inputs.
Inputs are user-entered figures. Results are planning estimates, not financial advice or a forecast. This tool is not affiliated with or endorsed by Amazon. Everything runs in your browser. Nothing you type is sent or stored.
FAQ
How do I calculate break-even ACOS?
Divide your per-unit contribution (price minus costs) by the price. That percentage is the break-even ACOS.
What ACOS is profitable?
Any ACOS below your break-even ACOS earns a profit on the first sale, before fixed costs. The gap between them is the profit as a share of sales.
Should I include fees and shipping in the margin?
Yes, if you pay them per unit. Use the costs that apply to your listing so the margin is what you actually keep before advertising.
Why is break-even ROAS the inverse of break-even ACOS?
ROAS is ad-attributed sales / ad spend and ACOS is ad spend / ad-attributed sales, so each is one divided by the other.