OpenAI and Anthropic count revenue differently, and investors are confused

OpenAI says its annualized revenue run-rate was approaching $50 billion as of late September 2026. A lot of investors had a different number in their heads: $70 billion. That $20 billion gap did not come from fraud, a leak, or a typo in a pitch deck. It came from two companies using two different methods for counting money that flows through cloud partners, and from investors who tried to make the figures comparable. Reports from the Financial Times and Bloomberg on October 8-9, 2026 laid out the confusion. The timing is awkward. Both OpenAI and Anthropic are being watched closely ahead of potential IPOs, and the market is trying to decide which one is bigger. Where the $70 billion came from Annualized revenue run-rate, or ARR, is a simple idea. You take a company’s current revenue pace and project it across a full year. The trouble starts with what counts as revenue in the first place. Both OpenAI and Anthropic sell their AI models directly. They also sell through cloud platforms such as Microsoft Azure and Google Cloud, where a business customer buys access through its existing cloud account. When a sale passes through a partner like that, a company has a choice to make. It can b...