Nobody has measured this well. That is the honest answer, and it is worth stating before the numbers start, because the figure most commonly cited for how many marketplaces a growing brand sells on traces back to a vendor blog post whose own arithmetic does not reconcile. What does exist is a set of adjacent statistics from sources that publish their methodology, and together they bracket the question closely enough to be useful. Here is what is known, who measured it, and which widely repeated numbers to throw away.
The size of the pool
The U.S. Census Bureau reported that e-commerce accounted for 17.1 percent of total retail sales in the second quarter of 2026, with adjusted e-commerce sales of $340.2 billion against total retail sales of $1,986.5 billion. That release, numbered CB26-133, came out on August 18, 2026, and the figure sits in Table 1 of the Quarterly Retail E-Commerce Sales report. The estimate is drawn from a stratified sample of roughly 10,800 retail firms, excluding food services, and covers employer firms only. Nonemployer businesses were removed from the series in the April 2025 benchmark revision, so comparisons against older versions of this number are not apples to apples.
Digital Commerce 360 put the same quarter at 23.5 percent in analysis published September 10, 2026. Both numbers are correct. Digital Commerce 360 excludes restaurants, bars, automobile dealers, gas stations and fuel dealers from the denominator, on the reasoning that those are dollars consumers could not realistically spend online. Census does not. Most roundups pick one of these at random and imply the other is wrong. They are measuring different things, and citing both with their denominators attached is more useful than picking a side.
How much of it runs through marketplaces
ECDB, in its Global E-Commerce Compass 2026 published in June 2026, reported that marketplaces accounted for 83.4 percent of global e-commerce gross merchandise value in 2025, up from 81.0 percent in 2023. The research covers business to consumer physical goods only, excluding B2B, digital services, subscriptions and consumer to consumer sales.
One framing caution that matters. ECDB tracks marketplaces at the platform level, meaning a platform’s entire GMV counts, including its own first party retail. So 83.4 percent describes how much commerce flows through marketplace platforms, not how much is sold by third party sellers. Those are different claims and the second one is much smaller.
On the third party question specifically, Amazon’s own supplemental financial disclosure for the second quarter of 2026, released July 30, 2026, reported that third party sellers accounted for 61 percent of worldwide paid units. The metric excludes Whole Foods Market. The six quarter trend has been flat, running between 60 and 62 percent since early 2025. Most secondary sources are still citing 60 percent, which was the first quarter figure.
How many sellers there are, and the direction of travel
Marketplace Pulse reported on April 16, 2026 that the active seller count on Amazon.com declined from 584,000 in January 2025 to 500,000 in March 2026. Marketplace Pulse counts a seller as active if the account received at least one customer feedback rating in the trailing year.
The same analysis found that fewer than 8,000 sellers now generate half of Amazon’s estimated $300 billion in U.S. third party GMV, down from roughly 15,000 sellers holding that position less than three years earlier. Concentration is increasing while the seller count falls.
Amazon’s own small business impact reporting, published April 30, 2026 and covering calendar 2025, states that U.S. independent sellers averaged more than $375,000 in annual sales, that more than 75,000 independent sellers surpassed $1 million in sales, and that over 11,000 U.S. based independent sellers grew sales by more than 10 times. This is Amazon’s internal platform data with no stated sample or external audit, so treat it as a company claim rather than a study. Note also that Amazon says 60 percent of sales in this document while reporting 61 percent of paid units in its financial disclosure. Sales and units are different metrics and the two figures are not interchangeable.
The closest anyone has come to the actual question
Two data points get near it, and both need caveats.
Marketplace Pulse reported on March 27, 2025 that 69 percent of Amazon sellers sell in just one marketplace, with fewer than 1 percent selling in eleven or more and 6 percent having expanded to six or more. The trap is that marketplace here means one of Amazon’s country marketplaces, so Amazon.com versus Amazon.de versus Amazon.co.jp. It says nothing about whether those sellers also list on Walmart or Shopify. The same analysis found 12 percent of U.S. sellers had expanded into Canada and 5 percent into Mexico.
Jungle Scout, in research published February 7, 2023 based on a survey of more than 2,000 Amazon sellers, found that 61 percent of Amazon sellers already sold on at least one other e-commerce platform, led by eBay, Shopify and Walmart. That is the cleanest direct answer available, and it is three and a half years old. Treat it as a floor rather than a current figure.
For cross platform overlap, Marketplace Pulse reported on March 28, 2024 that more than 50 percent of Walmart sellers also sell on Amazon, and at least 20 percent of Shein and Temu marketplace sellers also sell on Amazon and Walmart. The method matched sellers by normalized business name, and the author stated openly that the real overlap is likely higher than the measured figure.
What sellers themselves report
The Marketplace Pulse Seller Index, published April 2, 2026, surveyed 181 marketplace sellers representing more than $2 billion in combined annual revenue. Twenty three percent described themselves as thriving, 31 percent as grinding and 38 percent as distressed. Forty nine percent named marketplace fees as their primary margin concern and 47 percent reported a year over year margin decline.
The sample is small and self selected, which Marketplace Pulse states up front rather than burying. That disclosure is more than most vendor research offers.
Three numbers to stop citing
Mirakl’s 2026 Seller Report claims single marketplace sellers average $575,093 in GMV while sellers on two or more average $10,073,917, a 17.5 times multiplier. The figures do not reconcile with Mirakl’s own stated dataset. The same post says it analyzed over 100,000 sellers representing nearly $15 billion in annual GMV, which implies an average of roughly $150,000 per seller, while also claiming average GMV per seller has reached $7.5 million. Three mutually incompatible averages appear in one document, and the full report is gated. Setting that aside, the causation runs backwards anyway: large sellers expand onto more marketplaces because they are already large.
Omnisend’s figure that brands using three or more channels achieve a 287 percent higher purchase rate is the most repeated multi channel statistic in circulation and it does not apply here. The channels in question are marketing channels such as email, SMS and web push, not sales channels or marketplaces. The figure also appears simultaneously attributed to a 2020 analysis and to 2026 benchmark data with no published methodology for either.
Finally, the claim that Amazon has more than 6 million third party sellers comes from Marketplace Pulse research published in March 2021, and that source explicitly says most of those accounts are not active. Current active sellers on Amazon.com are approximately 500,000.
What this adds up to
Marketplaces dominate the channel mix, third party share of Amazon units has been stable around 61 percent for six quarters, the active seller population is shrinking while revenue concentrates, and the specific question of how many marketplaces a typical growing brand operates has no current, methodologically clean answer. The best available evidence puts a clear majority of Amazon sellers on at least one other platform, and that evidence is from 2023.
The operational consequence is the same regardless of the exact number. A brand on three or four marketplaces has three or four settlement formats, three or four fee structures and one inventory pool, which is the problem products like ConnectBooks, A2X and Webgility exist to solve. Anyone quoting you a precise average channel count should be asked where it came from.