SAN FRANCISCO » Facebook CEO Mark Zuckerberg reaped a gain of nearly $2.3 billion last year when he exercised 60 million stock options just before the online social networking leader’s initial public offering.

The windfall detailed in regulatory documents filed Friday saddled Zuckerberg, 28, with a massive tax bill. He raised the money to pay it by selling 30.2 million Facebook Inc. shares for $38 apiece, or $1.1 billion, in the IPO.

Facebook’s stock hasn’t closed above $38 since the IPO was completed last May. The shares gained 71 cents Friday to close at $26.85.

The 29 percent decline from Facebook’s IPO price has cost Zuckerberg nearly $7 billion on paper, based on the 609.5 million shares of company stock that he owned as of March 31, according to the regulatory filing. His current stake is still worth $16.4 billion.

Zuckerberg, who started Facebook in his Harvard University dorm room in 2004, has indicated he has no immediate plans to sell more stock.

The exercise of Zuckerberg’s stock options and his subsequent sale of shares in the IPO had been previously disclosed. The proxy statement filed to announce Facebook’s June 11 shareholder meeting is the first time that the magnitude of Zuckerberg’s stock option gain had been quantified.

The proxy also revealed that Zuckerberg’s pay package last year rose 16 percent because of increased personal usage of jets chartered by the company as part of his security program.

Zuckerberg’s compensation last year totaled nearly $2 million, up from $1.7 million last year. Of those amounts, $1.2 million covered the costs of Zuckerberg’s personal air travel last year, up from $692,679 in 2011.

If not for the spike in travel costs, Zuckerberg’s pay would have declined by 17 percent. His salary and bonus totaled $769,306 last year versus $928,833 in 2011.

Zuckerberg will take a big pay cut this year. His annual salary has been reduced to $1 and he will no longer receive a bonus, according to Facebook’s filing. That puts Zuckerberg’s current cash compensation on the same level as Google CEO and co-founder Larry Page, whose stake in his company is worth about $20 billion.

The Associated Press formula for determining an executive’s total compensation calculates salary, bonuses, perquisites, above-market interest that the company pays on deferred compensation and the estimated value of stock and stock options awarded during the year. The AP formula does not count changes in the present value of pension benefits or stock option gains such as those recognized by Zuckerberg did last year.