Anthropic had been founded by splitting away from OpenAI, but it’s now far surpassed OpenAI in revenue.

Anthropic booked about $17 billion in revenue in the September quarter, while OpenAI’s quarterly revenue crossed $10 billion for the first time. That puts the Claude maker roughly 70% ahead of the ChatGPT maker on the top line, just days before Anthropic is expected to list on the Nasdaq.

The two sets of numbers surfaced within about a week of each other, and they come from very different kinds of sources. That matters for how much weight each can bear.

The numbers

Anthropic’s figure comes from its own IPO paperwork. An amended S-1 filed with the SEC on November 2 shows third-quarter revenue of about $17 billion, up from roughly $1.4 billion a year earlier. The filing puts it at $16.96 billion, which is more than 11 times the year-ago quarter. Sequentially, revenue grew 47%, down from 144% in the second quarter.

OpenAI’s number is reported rather than filed. Bloomberg reported that revenue for the quarter ending in September rose almost 50% from the previous quarter to $10 billion, nearly triple the year-earlier figure. OpenAI told investors on a November 10 call that it had crossed $10 billion in a quarter for the first time. The Wall Street Journal and The Information reported that the year-ago quarter was $3.9 billion, and that second-quarter growth had been only 17-18%.

So OpenAI is accelerating while Anthropic is decelerating from a much higher base. Anthropic has led on quarterly revenue since the second quarter, when its revenue was about $11.6 billion.

An important caveat on accounting

The two figures are not perfectly like-for-like. Anthropic counts sales made through cloud partners such as AWS, Google Cloud and Microsoft Azure on a gross basis, booking the total end-customer spend as revenue and treating partner payouts as expenses. OpenAI, per reporting, only includes its share of some partner-generated sales.

The effect is large enough to move headlines. OpenAI’s annualized revenue was initially reported at nearly $70 billion in September, but reports later clarified it was about $50 billion. The roughly $20 billion difference came from recalculating OpenAI’s sales using Anthropic’s method. In other words, on Anthropic’s accounting OpenAI would look meaningfully bigger, though still behind. The debate over run-rate math is not new, and has been playing out for months.

Run-rate revenue

On annualized run-rate, Anthropic’s lead is similar in shape. The S-1/A filed November 10 puts Anthropic’s run-rate revenue at about $81 billion as of October 31, up $10 billion in a month. The company itself notes this is not a substitute for GAAP revenue.

OpenAI’s run rate stood at roughly $50 billion at the end of September, according to the Financial Times, and Bloomberg reported OpenAI expects to reach at least $70 billion by the end of 2026.

The picture was very different not long ago. Anthropic’s run rate was about $9 billion at the end of 2025, against more than $20 billion for OpenAI. By late May, The Information had Anthropic at about $45 billion against OpenAI’s $30 billion, the first sign the order had flipped.

Profitability: a very different picture

Neither company is comfortably profitable, but the gap in burn is stark.

Anthropic posted a $567 million operating loss in the quarter, including stock-based compensation, after an operating profit of $974 million in the second quarter. The swing was driven largely by $5 billion of compute bought on short-term commitments at a premium, plus about $2 billion in non-cash charges tied to a donation-matching program. Excluding stock compensation and charitable contributions, Anthropic’s adjusted operating profit was $2.5 billion, a 15% margin.

OpenAI’s adjusted operating loss was $10.9 billion, up from $10.1 billion in the second quarter. Its adjusted operating margin improved from -150% to -109%, and that figure excludes stock compensation of $2.6 billion. Because OpenAI’s number is adjusted and Anthropic’s headline loss is not, the two aren’t directly comparable, but even on Anthropic’s adjusted basis the direction is clear.

Anthropic’s headline net loss looks far worse, at $23.3 billion for the quarter, but $21.9 billion of that was a non-cash charge from revaluing convertible notes and derivatives as its valuation rose.

How else they compare

Valuation. Anthropic’s $65 billion Series H at a $965 billion post-money valuation in May made it worth more than OpenAI, which had closed a $122 billion round at $852 billion in March. OpenAI is now reportedly raising at around $1.25 trillion, but has raised less than half of a planned $30 billion so far.

Users and customers. This is where OpenAI is far ahead. ChatGPT has 1.2 billion weekly active users and 100 million paying subscribers, and its ad product hit a $1 billion annualized run rate in August. Anthropic’s base is far smaller but far more valuable per head: more than 11,900 customers spending $100,000 or more a year, up from about 950 a year earlier, account for 74% of its revenue.

Enterprise. OpenAI is closing in. CFO Sarah Friar said enterprise revenue doubled in the quarter and now matches consumer. But the shift toward Anthropic in business has been under way for some time: Ramp data showed it passing OpenAI in US business adoption in April, while earlier Ramp figures had Anthropic’s share of combined chat-subscription spend rising from about 10% to over 65% in a year. In the API market, Menlo Ventures data showed OpenAI’s enterprise share falling from 50% to 25% since 2023.

Compute. Anthropic’s spending on compute and infrastructure was $9.9 billion in the quarter, 58% of revenue, up from 48% in the second quarter. Its infrastructure and lease commitments total roughly $895 billion. That is the flip side of its growth, and a number IPO investors will weigh carefully.

What to watch

Anthropic is expected to price its IPO on November 18 and begin trading on November 19, with an indicated range of $70 to $78 a share. Reported valuation targets have shifted, with the company reportedly having trimmed its target from earlier talk of $2 trillion.

Public markets will be the first real test of whether a company with $17 billion in quarterly sales, slowing growth and nearly $900 billion in commitments is worth more than a rival with 1.2 billion users and a re-accelerating business. Anthropic was reported to be on track to turn a profit much faster than OpenAI, and a $2.5 billion adjusted operating profit sits comfortably against OpenAI’s $10.9 billion adjusted loss, even if the GAAP picture was a small loss this quarter. OpenAI’s own numbers, meanwhile, remain unaudited until it files publicly.