The fiat standard

"Today, like the currency of most nations, the dollar is (Money that the government declares to be legal tender although it cannot be converted into standard specie) fiat money without intrinsic value, which means that it has no backing and would be entirely worthless but for the fact that people have been persuaded to use and accept it as if it had worth."

...

"As of September 2004, it has been estimated that if all the gold held by the U.S. government (261.7 million ounces = 8 140 Mg) were again required to back the circulating U.S. currency ($733,170,953,704), gold would need to be valued at $2,800/ounce (90 $/g)."

Quoted from here.