To make this question answerable in a finite amount of time, let's simplify things and ask, "How much money is there in actual United States dollars?" Since the statistics for the U.S. are easy to come by, we can examine this question in a couple of different ways.
The first way to look at it might be, "How much cash is there in U.S. currency?" If you took all the bills and coins floating around today and added them all up, how much money would you have? All of that hard and easily liquidated currency is known as the M0 money supply. This includes the bills and coins in people's pockets and mattresses, the money on hand in bank vaults and all of the deposits those banks have at reserve banks [source: Hamilton]. According to the Federal Reserve, there was $908.6 billion in the M0 supply stream as of July 2009 [source: Federal Reserve]. That sounds like an incredible amount, but think about it this way: According to the CIA, there were 307,212,123 Americans alive that month [source: CIA]. If you took all the cash and divided it up equally, each person should have about $3,000 in cash on them (or stuffed under the mattress). Obviously, there's some money missing, but there's an easy explanation for that: The Federal Reserve says that at any given time, between one-half and two-thirds of the M0 money stock of U.S. dollars is held overseas [source: Federal Reserve].
M1 represents all of the currency in the M0 money supply, plus all of the money held in checking accounts and other checkable accounts, as well as all of the money in travelers' checks. In July 2009, the M1 money supply for U.S. dollars equaled about $1,655.6 billion [source: Federal Reserve].
All told, anyone looking for all of the U.S. dollars in the world in July 2009 could expect to find around $8.3 trillion in existence.
Even though the Fed can't say precisely where all the U.S. dollars are in the world, it does try to keep track of how much exists. Not every nation in the world has a well-established central bank, though. Find out why it's so difficult to track exactly how much money exists in the world on the next page.