Here's how much Mark Zuckerberg and his wife have already donated

Facebook CEO Mark Zuckerberg just announced with the birth of daughter Max that he and wife Priscilla Chan plan to donate 99% of their Facebook shares - about $45 billion at Facebook's current market value - to "advancing human potential and promoting equality."

He plans to sell no more than $1 billion in stock each year for the next three years, while retaining majority voting rights in the company.

That's a pretty tremendous chunk of money, and in line with Zuckerberg's decision to sign the "Giving Pledge" nearly five years ago when he was 26.

The pledge stipulates that signees will donate the majority of their wealth to philanthropic causes, and has other high-profile participants like Bill Gates, Warren Buffet, and Larry Ellison.

The decision also follows the couple's history of giving: They've already committed $1.6 billion to philanthropy.

Here's a history of the couple's recent donations:

• $120 million: 5-year commitment to support education in underserved communities in the Bay Area.
• $75 million: gift to the Zuckerberg San Francisco General Hospital, the "safety net" care provider in the city.
• $25 million: donation to the Centers for Disease Control and Prevention (CDC) to fight Ebola
• $100 million: gift to Newark Public School System

So, at Facebook's current stock price, Zuckerberg and Chan plan to donate $46.6 billion total, leaving about $450 million in stock left over.

The new donations will flow through the newly created Chan Zuckerberg Initiative, which will focus initially on issues like personalized learning, curing disease, connecting people, and building strong communities.

Facebook says that Zuckerberg and Chan made the decision to donate now, rather than later in their careers, because they're already thinking about the future and want to encourage others to do the same.

"We must make long term investments over 25, 50 or even 100 years," Zuckerberg says. "The greatest challenges require very long time horizons and cannot be solved by short term thinking."