But because he started his company in college, he's already amassed quite a fortune despite his young age. His net worth is around $74 billion (according to Forbes), which means he's amassed an average of $5.97 million per day. That's second only to Amazon founder Jeff Bezos, whose approximate $132 billion fortune averages out to about $6.8 million each day of his life.
Other tech entrepreneurs, like M co-founder Bill Gates, also started their careers young — Gates was the youngest billionaire ever in 1987, when he earned his first billion at age 31. But as he has aged, Gates has turned his attention to philanthropy — now, at age 62, Gates's lifetime average comes out to just about $4 million per day. Berkshire Hathaway's Warren Buffett, who has pledged much of his fortune to Gates' foundation, nets about $2.7 million a day at the age of 87.
Zuckerberg, too, has turned much of his Facebook fortune to other causes in recent years. He has sold about $3.38 billion of Facebook stock over the past six months, according to FactSet, mostly to put toward the Chan Zuckerberg Initiative, which invests in a broad range of causes including education, health care, affordable housing, immigration reform and criminal justice reform.
Zuckerberg said in September he would sell as many as 75 million Facebook shares (then worth $12.8 billion) for CZI over the following 18 months.
Despite scrutiny on Facebook's business practices, shares have risen 6 percent so far this year, more than Google.
— CNBC's Nick Wells contributed to this report.