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U.S. Series B Funding Nears $48 Billion as Smaller Rounds Become Scarcer
Series B funding is running at a multiyear high in dollars, but deal counts are falling as capital shifts toward large AI rounds.
U.S. Series B funding is approaching $48 billion so far in 2026, even as fewer companies are raising rounds. That split points to a market where the headline total says little about the experience of a typical startup: capital is gathering in a small number of very large financings, many tied to artificial intelligence.
Crunchbase data puts this year’s investment around the Series B stage at roughly $48 billion, the highest tally in years. Yet the number of rounds is below the year-ago level and is on track for a multiyear low. The combination matters: record-setting dollars can coexist with a thinner pool of funded companies when a few checks account for a large share of the total. The data also includes some financings with Series B characteristics that companies did not explicitly label as Series B.1
Smaller checks are losing ground
The change is visible at the lower end of the market. Fewer than one-third of deals in the analyzed sample were below $30 million this year. From 2021 through 2025, rounds under that threshold made up about half of deals, according to Crunchbase data. The sample covers U.S. Series B rounds of $1 million or more.2
Rounds under $10 million are especially uncommon: the sample counted just 26 so far in 2026. For companies that need a more modest Series B to extend their runway or reach their next operating milestone, that scarcity may make fundraising harder. The source data does not show why each company raised a particular amount or how many sought funding and did not close a round, so deal counts alone can’t establish how broad that pressure is.
The shift also changes what the aggregate funding figure can tell founders and finance teams. A larger total may suggest ample capital in the market, but it doesn’t mean that capital is equally available across company sizes, sectors, or fundraising needs. The distribution of rounds is an essential part of the story.
Large financings lift the total
At the other end of the range, at least 110 companies have raised $100 million or more around the Series B stage this year, roughly a quarter of all deals. The largest was a $12 billion financing for Prometheus, the physical AI startup launched last year by Jeff Bezos. Prometheus did not publicly describe the financing as a Series B; multiple reports, including an Axios post, characterized it that way.3
World Labs, the model developer led by AI pioneer Fei-Fei Li, raised $1 billion in February. Valar Atomics, a nuclear energy startup, also secured $1 billion in Series B funding across tranches this year, with Sequoia Capital as lead investor. These financings illustrate how a handful of very large rounds can shape a total measured in tens of billions.
AI dominates dollars and deal flow
Artificial intelligence accounts for about two-thirds of Series B funding so far in 2026, compared with about half of investment in 2025 going to companies in AI categories. AI companies also represent more than half of reported U.S. Series B deals this year. The trend is therefore visible both in the allocation of dollars and in the mix of companies closing rounds.
For investors, founders, employees, and customers, those two measures point to different parts of the shift. The funding share shows where the largest pools of capital are going; the deal share shows that AI companies are also prominent among recipients by count. Neither measure, by itself, establishes how well-funded companies will perform or how long current fundraising conditions will last.
A favorable market with a narrow opening
The figures suggest strong appetite for Series B financing, particularly for AI startups with demonstrated traction and substantial earlier funding at seed and Series A. But the market looks less welcoming to companies seeking smaller rounds. For founders, the practical question is not only whether capital is available, but whether the size and terms of available financing fit the business’s next needs.
Large rounds can give selected companies significant resources, while the shrinking share of smaller deals may leave other startups with fewer apparent options at this stage. That gap is a key risk in reading the total: the $48 billion figure captures the scale of investment, while falling round counts and scarce sub-$10 million financings show how unevenly it is distributed. The next useful signal will be whether smaller rounds regain share or funding remains concentrated in a limited number of outsized deals.
Related Crunchbase data
Illustration: Dom Guzman
May include rounds that have characteristics of Series B financings but were not explicitly announced as Series B deals.↩
Sample included U.S. Series B rounds of $1 million or more.↩
Prometheus did not publicly announce its $12 billion funding round as a Series B, but reports from multiple sources, including an Axios post, described it as Series B.↩
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