What will OpenAI's market capitalization be at the close of its first day of public trading, in billions of USD?

OpenAI’s valuation is anchored by its $852 billion post-money mark from early 2026 3 sources, and management reportedly views a sub-$1 trillion IPO valuation as a nonstarter 2 sources. The base case is structurally biased upward, driven by rapid fundamental growth—annualized revenue (ARR) topped $40 billion in August cnbc.com and is projected to scale toward a median of $65 billion by mid-2027 . Applying a mid-teens forward multiple comparable to Anthropic’s cnbc.com supports a public debut comfortably above $1 trillion. Balancing this hyper-growth against a sobering tech tape, a first-day close around $1,125 billion (median) is the most probable outcome for a successful debut . The right tail (P90 of $2,000 billion) requires a resurgence of AI exuberance and ARR compounding past $90 billion , incorporating the 38% probability of a step-change model restoring a massive capability premium before the IPO. The downside (P10 of $645 billion) reflects risks of a persistent AI capex bust 2 sources forcing a listing at a steep discount to previous private marks.