What Is the Formula for Calculating Break-Even ACoS?
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Quick answer
Break-even ACoS is a profitability threshold that shows the highest advertising cost of sale an Amazon seller can accept before ad spend begins to cut into profit. It is calculated by dividing gross profit per unit by the selling price and multiplying by 100. The result is the percentage of each sale that can be allocated to ads while still breaking even. This number gives advertisers a measurable limit for evaluating campaign performance.
If you manage Amazon Ads, this is often the first number to calculate before deciding whether a campaign is truly profitable. It turns a simple cost metric into a practical spending ceiling.
The unit economics behind the formula
Break-even ACoS uses two numbers from a product's unit economics: the selling price and the gross profit per unit. Gross profit per unit typically reflects the selling price minus Amazon fees, product cost, shipping, and other direct per-unit costs.
- Selling price: what the customer pays for the product before tax.
- Gross profit per unit: revenue remaining after direct per-unit costs are subtracted.
- Result: the maximum percentage of revenue that can go to advertising before profit reaches zero.
How to use break-even ACoS in campaign decisions
Actual ACoS below break-even means advertising is still contributing to profit. Actual ACoS above break-even means each sale is losing money after ad spend. That gap is useful for setting target ACoS, adjusting bids, and deciding which search terms to keep or negate.
- Compare reported ACoS to your break-even figure for each product or campaign.
- Set a target ACoS below break-even to preserve a profit margin.
- Track ACoS trends across accounts with Amazon Ads Dashboard by Todoza.
When this matters
Break-even ACoS becomes especially important when margins are thin, a product is highly competitive, or spending is increasing faster than sales. It also helps during launch periods when the goal may be visibility rather than immediate profit, but you still need a clear ceiling to avoid unplanned losses.
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Related guides
Once the formula is clear, the next step is to apply it consistently across your Amazon Ads accounts. For a more detailed look at cost inputs and campaign scenarios, revisit the parent guide on break-even ACoS calculations.