What Is ACoS on Amazon? The Complete 2026 Guide for Sellers

ACoS (Advertising Cost of Sales) is the percentage of ad-attributed revenue you spend on advertising. You calculate it by dividing ad spend by ad-attributed sales and multiplying by 100. A $200 spend that drives $800 in sales is a 25% ACoS. A lower ACoS means more efficient ad spend, but "good" depends entirely on your profit margin, not a universal benchmark.

ACoS tells you whether your Amazon advertising is making money or quietly losing it. Get it right and you scale profitably. Misread it and you either starve winning campaigns or pour budget into ones that never pay back. This guide covers what ACoS means, how to calculate it, what a good ACoS looks like for your margins, and how it fits alongside TACoS and ROAS.

What ACoS means on Amazon

ACoS stands for Advertising Cost of Sales. It measures how much you spend on advertising relative to the revenue those ads generate, expressed as a percentage.

A lower ACoS means you spend less to earn each dollar of ad-attributed sales. A higher ACoS means each sale costs you more in ad spend. That single number drives most day-to-day bidding and budget decisions inside an Amazon account.

The ACoS formula

The formula is simple:

ACoS = (Ad Spend ÷ Ad-Attributed Sales) × 100

Say you spend $200 on a campaign and it generates $800 in sales. Your ACoS is (200 ÷ 800) × 100, or 25 percent. You are spending 25 cents in advertising for every dollar of ad revenue.

The math is easy. The mistake sellers make is feeding it bad inputs. Leave out part of your ad spend or miscount attributed sales and the number lies to you, which leads to bidding decisions that quietly erode profit.

What counts as a good ACoS

There is no universal target. A good ACoS depends on your profit margin, where the product sits in its lifecycle, and how competitive your category is. Benchmarks vary widely between categories, and you can see how much in our breakdown of Amazon ACoS benchmarks by category.

The anchor is your break-even ACoS, the point where ad spend equals your profit margin on the product. If your margin before ad costs is 35 percent, then a 35 percent ACoS means you break even on advertised sales. Anything below that is profit, anything above it is a loss on those sales.

That reframes the whole question. A 30 percent ACoS is healthy on a 40 percent margin product and underwater on a 20 percent margin one. Always read ACoS against your margin, not against a number you saw in a blog post.

Lifecycle matters too. A new launch often runs a deliberately high ACoS to buy visibility and velocity early, then settles as organic ranking builds and fewer sales need to come from ads. That dynamic is the heart of the Amazon flywheel, where paid sales feed organic ranking over time.

ACoS vs. TACoS

ACoS only sees ad-attributed sales. It tells you nothing about the organic sales happening alongside your campaigns, which is why it can mislead you about the health of the business as a whole.

TACoS, Total Advertising Cost of Sales, measures ad spend against your total revenue, both ad-attributed and organic. It answers a bigger question: how dependent is this business on paid advertising? Our guide to the TACoS metric walks through the math and what different trajectories signal.

The trend is what matters. TACoS falling while revenue grows means your organic engine is strengthening and ads are doing less of the heavy lifting. TACoS flat or rising as you scale spend means advertising is buying revenue without building durable organic momentum underneath it.

ACoS vs. ROAS

ROAS, Return on Ad Spend, is the inverse of ACoS. It frames the same relationship as revenue per dollar of ad spend rather than cost as a percentage of revenue.

A 25 percent ACoS equals a 4x ROAS. Both describe identical performance. Some teams prefer ROAS because it speaks in growth terms, while ACoS speaks in cost terms. Our ROAS calculation guide covers how to translate between the two so a client using one metric never leaves you guessing.

How to lower your ACoS

Lowering ACoS comes down to spending less per sale or converting more of the traffic you already pay for. A few levers do most of the work.

Tighten keyword targeting so budget flows to terms that convert, and add negative keywords to stop paying for searches that never turn into sales. Wasted spend on irrelevant clicks is the most common reason ACoS runs high. Structuring this well across campaign types is the core of disciplined Amazon PPC management.

Then fix the listing, because advertising efficiency is capped by conversion rate. When your title, images, price, and reviews convert more of the clicks you buy, each sale needs fewer clicks and your ACoS drops without touching a single bid. Stronger listing optimization is often the highest-leverage ACoS lever there is, because the ad gets the click but the listing earns the sale.

Finally, give campaigns enough data before reacting. Adjusting bids on a few days of thin data produces statistically noisy decisions and over-optimization. Let performance accumulate, then act on the trend.

The bottom line

ACoS is the efficiency gauge for your ad-attributed sales, and it only means something when you read it against your margin and your goals. Pair it with TACoS to see the whole business, translate it to ROAS when that frames the decision better, and remember that the fastest way to a lower ACoS often runs through your listing, not your bids.

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Frequently asked questions

What is ACoS on Amazon?

ACoS stands for Advertising Cost of Sales. It measures how much you spend on advertising relative to the sales those ads generate, shown as a percentage. A lower ACoS means you are spending less to earn each dollar of ad-attributed revenue, which is why it anchors most bidding decisions.

How do you calculate ACoS?

Divide ad spend by ad-attributed sales, then multiply by 100. For example, $200 in ad spend that generates $800 in sales gives an ACoS of 25 percent. Track all spend and sales accurately, since small omissions can skew the figure and lead to poor bidding decisions.

What is a good ACoS on Amazon?

There is no universal number, since a good ACoS depends on your profit margin, product lifecycle, and competition. As a general guide, an ACoS under 20 to 25 percent is often considered healthy, but a new product launch may justify a higher figure to build visibility early.

What is the difference between ACoS and TACoS?

ACoS measures ad spend against ad-attributed sales only. TACoS, or Total Advertising Cost of Sales, measures ad spend against total revenue, including organic sales. TACoS gives a fuller picture of how dependent your business is on paid advertising over time.

How do you lower your ACoS?

Focus budget on high-converting keywords, add negative keywords to cut wasted spend, and optimize your listing so more clicks convert. Stronger conversion rates mean fewer clicks are needed per sale, which improves efficiency without requiring you to cut bids across the board.