How to Calculate Break-Even ACoS for Each Amazon Product

Break-even ACoS is the single most useful number in Amazon advertising, and one of the least calculated. It tells you the highest ACoS a product can run before every ad-attributed sale starts losing money. Without it, ACoS is just a percentage with no reference point.

This guide walks through the calculation per product, the costs that belong in it, and how to turn it into a target you can actually manage to.

The definition

Break-even ACoS is your profit margin per unit before advertising, expressed as a percentage of the selling price.

Break-even ACoS = (price - all non-ad costs per unit) / price

At that ACoS, the ad spend for a sale equals the profit that sale would have made without ads. Above it, each ad-attributed sale loses money. Below it, each one makes some.

ACoS itself is defined by Amazon as ad spend divided by attributed sales; see the Amazon Ads ACoS guide.

Step 1: use the price customers actually pay

Use the average selling price for the period, after coupons and promotions, not the list price. If 30% of units sell with a 10% coupon, your effective price is lower than the number on the listing, and so is your break-even.

Step 2: list every per-unit cost except ads

Include all of these, per unit:

• Referral fee. A percentage of the price, varying by category. Check the current rate on Amazon's pricing page.
• FBA fulfillment fee. A fixed amount per unit based on size and weight tier.
• Storage fees, averaged per unit sold. Monthly storage divided by units sold that month is a reasonable approximation.
• Landed product cost: factory price plus freight, duties, prep and inbound shipping, divided by units.
• Returns and refunds, as an average cost per unit sold.
• Packaging or inserts if they are not already in your factory price.

Leave out fixed costs such as software subscriptions for now. They matter for net margin, but they do not change with each additional ad-driven sale.

Step 3: do the arithmetic (illustrative example)

Here is a product with invented numbers to show the method:

• Average selling price: $29.99
• Referral fee (15%): $4.50
• FBA fulfillment fee: $5.10
• Storage per unit sold: $0.35
• Landed cost: $9.20
• Returns and refunds per unit: $0.70

Total non-ad cost = $4.50 + $5.10 + $0.35 + $9.20 + $0.70 = $19.85. Margin before ads = $29.99 - $19.85 = $10.14. Break-even ACoS = $10.14 / $29.99 = 33.8%.

If a keyword runs at 40% ACoS, you lose about $1.86 on each ad-attributed sale. At 25% ACoS, you keep about $2.64.

Step 4: decide your target, not just your break-even

Break-even is a ceiling, not a goal. Most sellers set a target ACoS below break-even that leaves room for the profit they want from each ad-driven sale.

Target ACoS = break-even ACoS - desired profit margin per ad sale

If you want to keep at least 10% of the price as profit on ad-driven sales, the target in the example becomes 23.8%.

There are legitimate reasons to run above break-even for a while: launching a new product, recovering rank after a stock-out, or defending a branded term. The important thing is to do it deliberately, with an end date and a budget limit, instead of discovering it at month end.

Step 5: calculate per product, then recheck

Break-even differs between products because prices, sizes and costs differ. A single account-wide break-even hides losses on your weaker products behind your strongest ones.

Recalculate when any of these change:

• Amazon updates its fee schedule.
• Your landed cost changes with a new production run, freight rate or tariff.
• You change price or start a recurring promotion.

Common mistakes

• Using margin after ads. That double-counts advertising and gives a break-even that is too low.
• Forgetting landed cost. Using the factory price alone overstates margin, sometimes by several points.
• Comparing break-even ACoS to TACoS. They answer different questions; see ACoS vs TACoS vs net margin.
• Setting one target for all targets. A branded keyword and a broad discovery keyword deserve different targets under the same break-even.

Turning the number into decisions

Once you know break-even per product, sort your ad targets by ACoS and mark every one above break-even with meaningful spend. Those are your first candidates for bid reductions, negatives or pauses. The next article, how to find wasted Amazon PPC spend, covers that review in detail.

How Sollo Central uses break-even ACoS

Sollo Central stores a break-even ACoS for each product and classifies each target against it, so you can see at a glance which ones are performing well, which need fixing, and which are awaiting your approval. On our co-founder's account, for example, the product break-even used is 15.5%. Proposals to raise or lower bids state the expected effect relative to that line, and you approve each one or set a standing approval for routine changes within limits you choose.