Microsoft owns roughly 27% of OpenAI, a stake valued at about $135 billion when the deal was struck. With OpenAI reportedly targeting a $1 trillion listing, that holding could be worth close to $270 billion — even as Microsoft trades as 2026's worst-performing "Magnificent Seven" stock.
Microsoft has the most riding on OpenAI's rumored $1 trillion valuation of any shareholder — yet its own stock is having the worst 2026 of any "Magnificent Seven" member. Shares are down about 19% this year and sit nearly 30% below their 52-week high, according to The Motley Fool. That disconnect frames the question the report runs through: whether the IPO math changes the buy case.
The stake math
When OpenAI restructured into a public benefit corporation last October, Microsoft disclosed that its investment represented roughly 27% of the company on an as-converted diluted basis, valued at approximately $135 billion. The same agreement extended Microsoft's technology rights through 2032 and added an OpenAI commitment to buy an additional $250 billion of Azure services.
Then came June. OpenAI confirmed it had filed confidential paperwork with the Securities and Exchange Commission for an initial public offering, the first formal step toward a listing. According to reporting from The New York Times, the company is now leaning toward a 2027 debut rather than late 2026, largely because CEO Sam Altman has reportedly refused to accept a valuation below $1 trillion.
Here is the number that matters. If OpenAI lists at $1 trillion, a 27% stake would be worth about $270 billion — roughly double the value implied when the deal was struck, and equal to about 9% of Microsoft's entire $2.9 trillion market capitalization. But the timing and price are rumored intentions, not commitments, and OpenAI will likely keep raising capital, which can dilute that percentage over time.
Meanwhile, the actual business
The long-term case does not rest on OpenAI. In its fiscal third quarter ended March 31, 2026, Microsoft's revenue rose 18% year over year to $82.9 billion, earnings per share climbed 23% to $4.27, and Azure and other cloud services revenue grew 40%.
That growth carries a heavy price tag. Microsoft expects about $190 billion in capital expenditures in 2026, and management said that figure includes roughly $25 billion from higher component prices, with memory chips caught in a global supply crunch. The stock now trades at about 23 times earnings and roughly 20 times forward earnings — a discount to the premium it commanded through most of the AI boom.
Source: The Motley Fool
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