What Is Amazon ACoS? A Complete Guide for Sellers

Your Amazon ACoS tells you how many cents you spent on advertising for every dollar those ads earned. A 25% ACoS means you spent $0.25 to generate $1 in ad sales. Whether that is good, acceptable, or unprofitable depends entirely on your margin , and on one factor most guides leave out entirely: your Buy Box win rate.

TL;DR: ACoS stands for Advertising Cost of Sale. It equals ad spend divided by ad revenue, expressed as a percentage. A good ACoS sits below your net profit margin , that is your break-even ACoS. Target ACoS is typically 5 to 10 percentage points below that. What most ACoS guides skip: sellers who win the Buy Box consistently show lower ACoS because their sponsored listings appear in higher-converting ad placements alongside their organic position, producing more clicks per dollar spent.

ACoS definition: advertising cost of sale

ACoS stands for Advertising Cost of Sale. It is the percentage of ad-attributed revenue you spent on advertising to generate that revenue.

ACoS is Amazon’s native efficiency metric for Sponsored Products, Sponsored Brands, and Sponsored Display campaigns. Amazon calculates it automatically and shows it in the Campaign Manager dashboard, updated daily.

A lower ACoS means your advertising is more efficient: you are spending fewer cents to generate each dollar in ad sales. A higher ACoS means more of your revenue is going back to Amazon in advertising fees.

ACoS is not the same as TACoS (Total Advertising Cost of Sale), which divides total ad spend by total revenue , including organic sales. TACoS gives a broader view of advertising efficiency across your entire business. ACoS measures only the efficiency of your paid campaigns in isolation.

How to calculate ACoS

ACoS = (Total ad spend ÷ Total ad revenue) × 100

The formula is straightforward. The inputs both come directly from Amazon’s advertising reports.

Worked example:

You run a Sponsored Products campaign for a product over 30 days. - Total ad spend: $320 - Total ad revenue (sales attributed to those ads within the attribution window): $1,600

ACoS = ($320 ÷ $1,600) × 100 = 20%

For every dollar in ad sales this campaign generated, you spent $0.20 on advertising.

Where to find your ACoS in Seller Central:

Navigate to Advertising, then Campaign Manager. Your ACoS appears in the column next to your spend and sales figures. Filter by campaign, ad group, keyword, or individual product. The default attribution window is 7 days for clicks , meaning a sale within 7 days of an ad click counts toward that ad’s ACoS calculation.

A note on ACoS vs net margin:

ACoS measures efficiency against ad revenue, not against all costs. A 20% ACoS does not mean you made 80 cents of profit per dollar of ad sales , you still owe Amazon its referral fee, FBA fulfilment fee, and your landed cost on every unit. Always compare your ACoS to your net margin, not to 100%.

What is a good ACoS on Amazon? Category benchmarks

A good ACoS is one that sits below your break-even ACoS. Your break-even ACoS equals your net profit margin , the percentage of each sale that is left after all costs.

If your net margin is 25%, your break-even ACoS is 25%. Spend more than 25% of ad revenue on ads, and those ad sales cost you money. Spend less, and they produce net profit.

That means “good ACoS” is a seller-specific answer, not a universal number. A seller with a 30% margin and 20% ACoS is running profitable ads. A seller with a 15% margin and 20% ACoS is losing money on every ad sale.

General ACoS ranges by competitive intensity (2026):

These ranges reflect general competitive patterns rather than confirmed per-category data. Your exact ACoS benchmark is your own net margin, not an industry average.

The launch ACoS exception:

New listings often run above break-even ACoS for the first 60 to 90 days. At launch, every ad sale builds ranking velocity, review accumulation, and organic position , all of which reduce the need for paid traffic over time. Running a 40% ACoS on a 25% margin product is a loss on each ad sale during launch, but it buys organic position that generates profitable sales without ads later.

The connection between ACoS and your Buy Box win rate

Sellers with higher Buy Box win rates consistently achieve lower ACoS. The mechanism is not intuitive but it is direct: winning the Buy Box determines where your sponsored ads appear on the product page.

According to WebFX (citing Wiser data), the Amazon Buy Box accounts for 82% of all sales on the platform. That is the featured offer position , the “Add to Cart” button at the top right of every product page. It is also the position where Sponsored Products ads receive their highest-converting placement.

When your listing holds the Buy Box, your Sponsored Products ads appear adjacent to the primary purchase button , in the position buyers are already looking at when they decide to buy. When a competitor holds the Buy Box, your ads appear in lower-priority positions further down the page.

The result: Buy Box winners get more clicks per dollar of ad spend than non-winners on the same listing. More clicks at the same spend produces more conversions at the same cost, which lowers ACoS.

Jungle Scout’s seller research shows that margins and advertising costs are the top two profitability concerns for Amazon sellers. The connection between the two runs directly through Buy Box win rate , a factor most ACoS optimisation guides never address.

How repricing affects your ACoS , the link most sellers miss

Repricing affects ACoS through its effect on Buy Box win rate. A correctly configured repricer wins more Buy Box time. More Buy Box time means ads appear in better positions. Better positions produce lower ACoS.

The chain:

Repricing raises your Buy Box win rate by keeping your price competitive without falling below your floor. A seller stuck at their minimum price while the market allows $2 more wins less Buy Box time than a seller whose ceiling-hunt rule finds the highest price at which rotation holds.
Higher Buy Box win rate means more time in the primary ad slot. Sponsored Products in the Buy Box slot receive dramatically higher CTR than the same ads lower on the page.
Higher CTR at the same bid means more conversions per dollar. Your cost-per-click stays the same, but each click is more likely to convert because it comes from a buyer already oriented toward purchasing.
More conversions at the same spend lowers ACoS. The formula has not changed , the denominator (ad revenue) grows while the numerator (ad spend) holds steady.

The reverse also holds. A poorly configured repricer that races to the floor compresses the average selling price, reduces Buy Box win rate when competitors hold the Box at a price your floor prevents, and pushes sponsored ads into lower-converting positions. The same campaign spend generates fewer conversions. ACoS rises.

This is why ACoS optimisation and repricing configuration are the same conversation, even though most sellers treat them as separate workstreams.

For the mechanics of how Amazon’s Buy Box algorithm weighs price against other factors, the Buy Box guide covers the full scoring model.

Book a Demo , win more Buy Boxes to lower your ACoS and see how Repricer.com’s analytics connect both metrics in a single dashboard.

Target ACoS vs break-even ACoS

Break-even ACoS is the ACoS at which your ad sales generate zero profit. Target ACoS is the ACoS at which your ad sales generate your required profit margin.

Break-even ACoS = your net profit margin %

Example: A product with a 30% net margin has a break-even ACoS of 30%. At 30% ACoS, every dollar of ad sales generates exactly zero net profit , all the margin goes to the ad spend.

Target ACoS = break-even ACoS minus your required return

If you need a 10% return on ad sales, your target ACoS is 20% (break-even ACoS 30% minus 10%).

Calculating your break-even ACoS:

You need your all-in cost per unit and your average selling price.

Example: - Average selling price: $24.99 - Amazon referral fee (8%): $2.00 - FBA fee: $3.18 - Landed cost (unit + freight + duties): $9.00 - Returns provision: $0.45 - Inbound shipping: $0.45 - Total costs: $15.08 - Net margin: $24.99 − $15.08 = $9.91 or 39.7% - Break-even ACoS: 39.7%

At 39.7% ACoS, this seller’s ad sales generate zero profit. At 25% ACoS, each ad sale generates 14.7% margin , a healthy return on advertising.

Note: the break-even ACoS calculation above excludes advertising spend from the cost stack, because the advertising cost is what ACoS itself measures. Including it would create a circular calculation.

For the full cost stack that feeds into your margin and therefore your break-even ACoS, the Amazon seller fees guide covers every line item.

How to improve your ACoS by improving Buy Box performance

Three actions lower ACoS through Buy Box improvement rather than through bid adjustments alone.

Action 1: Audit your Buy Box win rate by ASIN. Pull your Buy Box percentage from Seller Central (Reports, then Business Reports, then Detail Page Sales and Traffic, then Featured Offer Percentage column). Any ASIN with a win rate below 30% on a competitive listing where you are running Sponsored Products is a candidate for repricing reconfiguration , lower win rate means more of your ad spend is going to lower-converting placements.

Action 2: Switch from “undercut” repricing rules to “match Buy Box” rules. Undercut rules chase competitors downward and often produce price oscillation that reduces your Buy Box win time without lowering your ACoS. Match rules keep your price competitive without triggering spiral dynamics. More stable Buy Box holding, better ad placement, lower ACoS.

Action 3: Ensure your floor is calculated from current costs. A floor set below your real break-even costs you money on every sale at the minimum , but a floor set above the competitive range keeps you out of Buy Box rotation entirely. Both outcomes hurt ACoS: one by eroding margin, the other by pushing ads into lower-converting positions. A correctly calculated floor is the foundation of both Buy Box performance and ad efficiency.

For how to read win rate and average selling price together in your repricing analytics, the Buy Box win rate guide covers the specific metrics to pull each week.

Key Takeaways

ACoS = (ad spend ÷ ad revenue) × 100. Find it in Campaign Manager, updated daily. Evaluate it against your margin, not against an industry benchmark.
Break-even ACoS = your net profit margin. Below break-even means ads are profitable. Above means they are not.
Buy Box win rate directly affects ACoS. Sponsored Products in the Buy Box slot generate higher CTR than ads in lower positions. More Buy Box time means more efficient ad spend.
Repricing and ACoS optimisation are the same conversation. A repricer that improves Buy Box win rate at the right price improves ad placement quality, which lowers ACoS without touching your bids.
Launch ACoS above break-even is often correct. The ranking and review velocity those ad sales build generate profitable organic sales later. Evaluate ACoS against your business phase, not only against break-even.

Action Plan

Calculate your break-even ACoS today. Pull your all-in cost per unit (landed cost + FBA fee + referral fee + inbound + returns provision). Subtract from your average selling price. The result as a percentage of selling price is your break-even ACoS. Any campaign running above this figure is losing money on ad sales.
Pull your Buy Box percentage for your top 10 ad-supported ASINs. Find the correlation: ASINs with lower Buy Box win rates likely show higher ACoS. These are the repricing-first optimisation opportunities.
Check whether your repricing rule type is contributing to Buy Box instability. Undercut rules create oscillation. Match rules create stability. Switch the rule type on ASINs where ACoS is high and win rate is volatile.
Set your target ACoS. Break-even ACoS minus your required margin return. For mature products: 5 to 10 percentage points below break-even. For launch-phase products: above break-even is acceptable for 60 to 90 days.
Review the Buy Box win rate and ACoS together monthly. Improvements in one should drive improvements in the other. If they diverge , win rate up but ACoS unchanged , investigate whether your ad placements are actually improving by checking the Placement Report in Campaign Manager.

Frequently Asked Questions

What is ACoS on Amazon?

ACoS stands for Advertising Cost of Sale. It is the percentage of ad-attributed sales revenue that you spent on advertising to generate those sales. Calculate it as: (ad spend ÷ ad revenue) × 100. A 25% ACoS means you spent $0.25 for every $1 earned through ads. Amazon calculates and displays ACoS automatically in Campaign Manager for Sponsored Products, Sponsored Brands, and Sponsored Display campaigns.

How do I calculate my Amazon ACoS?

Divide your total ad spend by your total ad-attributed revenue, then multiply by 100. Example: $400 spend on $2,000 in ad sales = 20% ACoS. Both numbers are available in your Campaign Manager dashboard. Set the date range, select the campaign or keyword level view, and read the ACoS column directly. Amazon uses a 7-day click-attribution window by default, meaning a sale within 7 days of an ad click counts toward that ad’s revenue.

What is a good ACoS percentage?

A good ACoS is one below your break-even ACoS, which equals your net profit margin percentage. If your net margin is 28%, any ACoS below 28% means your ad sales are profitable. There is no universal “good” ACoS number , a 35% ACoS is excellent for a seller with a 45% margin and ruinous for a seller with a 25% margin. During a launch phase, running above break-even ACoS for 60 to 90 days is often deliberate, as the ranking and review velocity generated by ad sales produce profitable organic traffic later.

How does repricing affect my Amazon advertising costs?

Repricing affects ACoS through its effect on Buy Box win rate. According to WebFX (citing Wiser), the Amazon Buy Box accounts for 82% of all sales on the platform. Sponsored Products ads appear in their most valuable position , adjacent to the featured offer button , only when your listing holds the Buy Box. More Buy Box time means ads appear in better positions, generating higher CTR at the same bid level. Higher CTR means more conversions per dollar spent, which lowers ACoS. A repricer that improves Buy Box win rate at the right price improves ad placement quality without requiring any bid changes.

What is the difference between ACoS and TACoS?

ACoS (Advertising Cost of Sale) divides ad spend by ad-attributed revenue only. It measures the efficiency of your paid campaigns in isolation. TACoS (Total Advertising Cost of Sale) divides total ad spend by total revenue , including organic sales not attributed to any ad click. TACoS gives a more complete picture of how advertising investment relates to overall business performance. A product with strong organic ranking will show a much lower TACoS than ACoS, because organic sales grow the denominator without requiring additional ad spend. For mature products with established organic ranking, TACoS is the more useful long-term efficiency metric.

Book a Demo , win more Buy Boxes to lower your ACoS and connect your repricing performance to your advertising results in Repricer.com’s analytics dashboard.