BY GEOFFREY A. FOWLER

Facebook Inc.'s impending initial public offering could yield 27-year-old founder Mark Zuckerberg a fortune valued at $21 billion to $28 billion.

According to IPO paperwork Facebook filed Wednesday, Mr. Zuckerberg owns about 28% of the soon-to-be-public company, and is its single largest shareholder. If Facebook raises money at a high-end valuation of $100 billion, Mr. Zuckerberg's stock would be worth $28 billion.

On top of his stock, last year Mr. Zuckerberg was paid $1.49 million in salary, bonus and other compensation for his role as chief executive, according to the regulatory filing.

Facebook's filing added that Mr. Zuckerberg will sell ...