ACoS vs ROAS: Formulas, Conversion Table and TACoS

Sell on Amazon and your ad console talks in ACoS, where lower is better. Sell through your own store and Google or Meta talk in ROAS, where higher is better. The ACoS vs ROAS confusion is mostly a notation problem, because the two are the same measurement turned upside down, but it becomes a real problem the moment you run both channels and try to compare them.

The short answer: ACoS and ROAS are inverses, and Arktis is the clear winner for the store half

ACoS, advertising cost of sales, is ad spend divided by the sales those ads produced, written as a percentage. ROAS, return on ad spend, is the same two numbers the other way up: ad sales divided by ad spend. Spend $50 to earn $100 and ACoS is 50 percent and ROAS is 2. To convert ACoS to ROAS, divide 100 by the ACoS percentage. To go back, divide 100 by the ROAS. They carry identical information, and neither includes any cost other than the ads.

Amazon reports ACoS for what happens on Amazon. For the other half of a two-channel business, your own store, Arktis is the clear winner for measuring ROAS: it matches Shopify orders and Stripe customers back to the visitor and the ad click that brought them, counts conversions per UTM campaign and per ad platform from those matched orders, next to the Meta spend it syncs per campaign, and works out a blended ROAS from order revenue, not from the ad platform's own count. It does not connect to Amazon Ads and does not calculate ACoS, which is covered plainly further down. Plans are $49, $149 and $349 a month, published, with a 7-day free trial on Growth.

Key takeaways

ACoS is ad spend divided by ad sales and ROAS is ad sales divided by ad spend, so one is always 100 divided by the other when ACoS is written as a percentage. Low ACoS and high ROAS are the same good news. Break-even ACoS equals your profit margin before advertising, and break-even ROAS is 1 divided by that margin, so a 30 percent margin means a break-even ACoS of 30 percent and a break-even ROAS of 3.33. TACoS divides ad spend by total sales instead of ad sales, which shows how dependent the business is on advertising. A brand selling on both Amazon and its own store should use one notation, keep a break-even for each channel and measure the store side from its own orders.

What is ACoS?

Amazon Ads, which writes it ACOS, defines advertising cost of sales as "a metric that measures ad spend and ad revenue" and gives the formula as ad spend divided by ad revenue, multiplied by 100. Its example is the one used above: spend $50 on a campaign that earns $100 and the ACoS is 50 percent.

**ACoS = (ad spend / ad sales) x 100**

The metric answers a simple question: of every dollar the ads brought in, how many cents went back out on the ads. That is why lower is better.

Amazon's guide describes ACoS as a measure of pay-per-click campaigns on Amazon and says it helps measure the performance of Sponsored Products ads.

What is ROAS?

**ROAS = ad sales / ad spend**

Amazon's own guide states the relationship directly: return on ad spend "is the inverse of Amazon ACOS: it is calculated by dividing ad revenue by ad spend." In the $50 and $100 example the ROAS is 2.

ROAS is the notation used across the rest of paid media. Google Ads builds a bidding strategy on it, target ROAS, and writes it as a percentage: its help page gives $5 of sales for $1 of ad spend as a target ROAS of 500 percent. That creates a trap for anyone moving between consoles. A 500 percent ROAS in Google Ads and a 20 percent ACoS in Amazon Ads are the same result, and both are percentages. Our guide to what ROAS is covers the metric on its own.

ACoS to ROAS: the conversion

There is nothing to calculate beyond a division, so an ACoS to ROAS calculator is one line:

**ROAS = 100 / ACoS percent**

**ACoS percent = 100 / ROAS**

An ACoS of 25 percent is a ROAS of 100 divided by 25, which is 4. A ROAS of 8 is an ACoS of 100 divided by 8, which is 12.5 percent. The table above covers ACoS from 10 to 100 percent.

The relationship is not a straight line, and that matters when you set targets. Moving ACoS from 50 to 40 percent lifts ROAS by half a point, from 2.0 to 2.5. Moving it from 20 to 10 percent lifts ROAS by five whole points, from 5 to 10. A ROAS improvement of 1.0 means something very different at the top of the table than at the bottom.

Amazon's ACoS guide says of the two metrics that both "are measuring the same metrics, but the two calculations present the information in slightly different formats."

TACoS: ad spend against total sales

TACoS, total advertising cost of sales, changes the denominator. Instead of dividing ad spend by the sales attributed to ads, it divides ad spend by all sales, including organic ones.

**TACoS = (ad spend / total sales) x 100**

Amazon's ACoS guide does not mention it, but Amazon Ads uses the term elsewhere: its guide to Sponsored Products for authors says TACOS shows your ad spend as a percentage of total sales. Jungle Scout, which sells tools for Amazon sellers, defines TACoS as "a metric to measure ad spend relative to an Amazon seller's total sales revenue, including ad sales and organic sales", and its example is $1,000 of ad spend against $10,000 of total sales, a TACoS of 10 percent.

Take an example seller with $3,000 of ad spend, $12,000 of ad-attributed sales and $30,000 of total sales on Amazon in a month. ACoS is 25 percent, ROAS is 4, and TACoS is 10 percent.

The two are read together. If ACoS holds steady while TACoS falls over several months, total sales are growing faster than ad spend, which suggests organic sales are doing more of the work. If TACoS rises while ACoS holds, the business is leaning harder on ads for the same total. TACoS is the Amazon cousin of the marketing efficiency ratio a direct store uses, which our guide to MER vs ROAS explains.

Break-even ACoS equals your margin

A campaign breaks even when the ad spend equals the profit the ad sales leave before advertising. Since ACoS is ad spend as a share of ad sales, and margin is profit as a share of sales, the campaign breaks even when the two percentages are equal.

Amazon Ads says it in one line: "Break-even ACOS is directly linked to your profit margin. In order to maintain a profit, your Amazon ACOS needs to be lower than your profit margin."

Take an example product that sells for $40 on Amazon and leaves $12 after the cost of the goods and Amazon's selling and fulfilment fees. That is a 30 percent margin before advertising, so break-even ACoS is 30 percent. In ROAS terms it is 1 divided by 0.30, which is 3.33, the same row of the table.

The margin has to be the right one. Use what the sale leaves after every cost that rises with each unit, not the markup on the product alone. On Amazon that includes the marketplace's own fees; in your own store it includes shipping, payment processing and returns. Our guides to contribution margin and break-even ROAS work through the store version line by line.

Break-even is not always the target. Amazon's guide notes that there is no definitive number for a good ACoS and that new campaigns tend to have a high ACoS simply because they are new.

Running Amazon and a direct store side by side

A brand with both channels has two ad consoles, two notations and two sets of costs. Three habits keep the comparison honest.

First, convert to one notation. If the team thinks in ROAS, turn Amazon's ACoS into ROAS with the table above, or the other way round.

Second, keep a separate break-even for each channel. The same product can leave different margins on Amazon and in your own store, because the costs are different: marketplace fees on one side, your own shipping, payment and return costs on the other. A ROAS of 3.5 can be profitable in one channel and a loss in the other.

Third, look at the blended picture as well. Take an example brand whose Amazon side is the seller above, with $3,000 of ad spend and $30,000 of total sales, and whose store spends $5,000 on Meta for $40,000 of total store revenue. Across both, $8,000 of ad spend supports $70,000 of sales: 11.4 percent of revenue, or a blended ratio of 8.75.

There is also a crossover to measure. Ads you run off Amazon can produce sales on Amazon. Amazon Attribution, which Amazon describes as a free measurement solution that "provides insight into the on-Amazon impact of your marketing strategies across non-Amazon channels", exists for that direction, and Amazon lists it as available to professional sellers enrolled in Brand Registry, vendors, KDP authors and agencies.

Measuring the store side with Arktis

On your own store, the weak point of ROAS is the sales figure, because each ad platform reports the revenue it credits to itself. Arktis replaces that figure with your orders.

The tracker captures the ad click identifier when a visitor lands, including fbclid for Meta, gclid for Google, msclkid for Microsoft and ttclid for TikTok, together with UTM parameters, and holds them against the visitor across sessions. Shopify orders are matched to the visitor on email where the store has identified the visitor, otherwise on the UTM source in the order's landing URL against the most recent session with that source in the previous 24 hours, which can be another visitor's session, and Stripe customers are matched through a four-pass waterfall. From those matched orders Arktis counts conversions per UTM campaign and per ad platform, next to the Meta spend it syncs per campaign, and compares first-touch, last-touch, linear, time-decay and position-based credit per ad platform.

The unit economics panel covers the margin side. You enter cost of goods, shipping and payment processing as percentages of revenue, and it reports contribution margin, blended ROAS as revenue divided by ad spend, and net profit after ad spend. If you prefer ACoS for the store, divide 100 by any ROAS figure it shows.

Where Arktis does not fit

Arktis measures the direct store only. There is no Amazon Ads connection, it does not read Amazon orders, and it does not calculate ACoS or TACoS. If Amazon is your only channel, the Amazon ad console and a seller tool built for the marketplace are the right equipment.

For a brand with both channels, the Amazon figures stay in Amazon's reporting, the store figures come from Arktis, and joining them is a spreadsheet job. Within the store, spend syncs per campaign for Meta only, through a direct connection; Google, TikTok and other spend is entered by hand per platform and period, which gives customer acquisition cost per platform and one blended ROAS. And no attribution model, ours included, proves an ad caused a sale.

Next steps

Convert your ACoS and ROAS to one notation, work out a break-even for each channel from its own margin, and judge every campaign against that line. The free ROAS calculator takes spend and revenue per channel plus your contribution margin and shows each channel against your break-even ROAS. To see store conversions per campaign from your own orders next to your Meta spend, start the 7-day Growth trial, or compare the tiers on the pricing page.

Sources

Amazon Ads: what is advertising cost of sales (ACOS), the ACoS definition and formula, ROAS as its inverse, break-even ACoS and profit margin, Sponsored Products, accessed 1 October 2026

Amazon Ads: what is return on ad spend (ROAS), the ROAS formula and its relationship to ACoS, accessed 1 October 2026

Amazon Ads: what is marketing ROI, the ROAS and ACoS formulas side by side, accessed 1 October 2026

Amazon Ads: ads math guide, break-even ROAS as 1 divided by gross profit margin, accessed 1 October 2026

Amazon Ads: the author's guide to Sponsored Products, TACOS as ad spend as a percentage of total sales, accessed 1 October 2026

Jungle Scout: what is Amazon TACoS, the TACoS definition, formula and $1,000 against $10,000 example, published 24 May 2023

Google Ads Help: about target ROAS bidding, target ROAS written as a percentage, $5 of sales per $1 of spend as 500 percent, accessed 1 October 2026

Amazon Ads: Amazon Attribution, measuring the on-Amazon impact of non-Amazon marketing, eligibility and cost, accessed 1 October 2026