FACTBOX-List of US billionaires making charity pledge

(Reuters) - A group of U.S. billionaires pledged Wednesday to give away at least half of their wealth to charity as part of a campaign led by investor Warren Buffett and Microsoft founder Bill Gates.

Wednesday's commitments bring to 40 the number of billionaires giving away half their wealth. Many of those listed have already been engaged in significant philanthropic efforts. Below are details on how much they are worth, based on data from Forbes magazine, and how they made their fortune.

Bill and Melinda Gates -- founder of software giant Microsoft and the Bill and Melinda Gates Foundation; worth $53.5 billion.

Warren Buffett -- famed investor who made his fortune through his Berkshire Hathaway firm, which buys companies he sees as undervalued; worth $47 billion

Eli Broad -- the real estate and construction billionaire founded home builder Kaufman & Broad, worth $5.7 billion; has already given more than $2 billion to The Broad Foundations; worth $5.9 billion.

John Doerr -- venture capitalist with Kleiner Perkins Caufield & Byers who made millions with early bets on Amazon, Netscape and Sun Microsystems and became a billionaire with Google; worth $1.7 billion.

Gerry Lenfest -- the media entrepreneur has already given away more than $800 million, or about 65 percent of his fortune, a spokeswoman said.

John Morgridge -- Former Cisco Systems chairman now focuses on philanthropy; worth $1.6 billion.

Paul Allen -- Founded software giant Microsoft with Gates; worth $13.5 billion.

Laura and John Arnold -- John Arnold worked as a high-flying trader at Enron and then founded hedge fund Centaurus Energy; worth $4 billion.

Michael Bloomberg -- the mayor of New York City made his fortune by founding the news and information company which bears his name, Bloomberg LP; worth $18 billion.

Michele Chan and Patrick Soon-Shiong -- Patrick is the son of a village doctor in China who made his fortune on cancer treatments and generic drugs; worth $5 billion.

Barry Diller and Diane von Furstenberg -- Diller made his fortune on the Home Shopping Network while wife von Furstenberg is a renowned fashion designer; worth $1.2 billion.

Larry Ellison -- founder of database giant Oracle; worth $28 billion.

Barron Hilton -- Son of hotel legend Conrad Hilton who built his father's hotel empire; worth $2.5 billion.

Jon and Karen Huntsman -- Jon is worth $1 billion, made by turning Huntsman Corp from a fast-food container supplier into America's largest private chemical company.

Joan and Irwin Jacobs -- Founded Qualcomm, which commercialized CDMA digital wireless technology; worth $1.2 billion.

George Kaiser -- His Kaiser-Francis Oil is among the world's biggest private energy producers and owns $2 billion stake in Bank of Oklahoma; worth $10 billion.

Elaine and Ken Langone -- Ken is an investment banker who took Ross Perot's Electronic Data Systems public in 1968 and was an early investor in Home Depot; worth $1 billion.

Lorry Lokey -- Founded Business Wire, which disseminates press releases and was bought by Berkshire Hathaway, freeing Lokey to focus on philanthropy.

George Lucas -- the "Star Wars" movie maker and owner of famed Hollywood special effects company; worth $3 billion.

Alfred Mann -- made $1.4 billion in medical devices.

Bernie and Billi Marcus -- Bernie started Home Depot after getting fired by the now defunct Handy Dan; worth $1.5 billion.

Thomas Monaghan -- founded Domino's Pizza and one-time owner of the Detroit Tigers, sold Domino's in 1998 and has since worked on philanthropy.

Pierre and Pam Omidyar -- Pierre made his fortune launching online auction company eBay; worth $5.2 billion.

Bernard and Barbro Osher -- Bernard was a founding director of World Savings, which merged with the Wachovia Corp and bought auction house Butterfield & Butterfield, which he sold to eBay. Has been a long-time philanthropist.

Ronald Perelman -- made his fortune in leveraged buyouts of companies such as Revlon; worth $11 billion.

Peter Peterson -- co-founded private equity outfit Blackstone Group and the Peter G. Peterson Foundation; worth $2 billion.

T. Boone Pickens -- made his $1.1 billion in oil and gas investments.

Julian Robertson Jr. -- made $2.2 billion in hedge funds.

David Rockefeller Sr. -- Philanthropist grandson of oil baron John D. Rockefeller; worth $2.2 billion.

David Rubenstein -- co-founded private equity giant Carlyle Group; worth $2.5 billion.

Herb and Marion Sandler -- the couple were co-CEOs of thrift Golden West, which was sold to Wachovia in 2006. The couple owned a 10 percent stake in the company and gave $1.3 billion away to their Sandler Foundation.

Vicki and Roger Sant -- Roger co-founded global energy company AES and the couple have long been Washington philanthropists, known for bringing Chinese pandas to the National Zoo, among other high-profile donations.

Walter Scott Jr. -- Made his $1.9 billion in construction and telecoms.

Jim and Marilyn Simons -- Jim founded quantitative hedge fund Renaissance Technologies; worth $8.5 billion.

Jeff Skoll -- eBay's first president and full-time employee; worth $2.4 billion.

Tom Steyer and Kat Taylor -- worth $1.2 billion in 2008, the asset manager and his wife founded OneCalifornia Bank, a community development bank, and have given for research on sustainable and renewable energy.

Jim and Virginia Stowers -- Jim is the mutual fund tycoon who started what became the American Century fund family. The couple have given $1.9 billion to the Stowers Institute for Medical Research which performs genetic research.

Ted Turner -- Founded CNN cable news channel and is worth $1.8 billion after already giving $1.5 billion to charity.

Sanford and Joan Weill -- Sanford is the former chief executive of Citigroup; the couple have given more than $250 million to Cornell's medical school, now known as the Weill Cornell Medical College.

Shelby White -- New York philanthropist and and widow of late billionaire investor Leon Levy. (Reporting by Mark Egan in New York, editing by Bill Trott)