Why Is the U.S. Dollar the World's Reserve Currency? From Bretton Woods to Today

The dollar leads thanks to the size of the U.S. economy, deep financial markets and the legacy of Bretton Woods. See what a reserve currency is and the latest IMF reserve data.

Curious Mundi Editorial Team · November 4, 2026

Illustration of a globe with a gold coin at its center and trails of coins flowing toward it from four directions.

The U.S. dollar is the world's main reserve currency because it combines one of the largest economies, large and liquid financial markets and institutions investors trust. History helped too: the 1944 Bretton Woods agreement put the dollar at the center of the postwar monetary system. Today it still makes up more than half of global foreign exchange reserves.

That does not make the dollar the most "valuable" currency per unit, or the one people use most in their daily shopping around the world. Its lead shows up elsewhere: in central bank reserves, foreign exchange trading, cross-border debt and international lending.

What is a reserve currency?

According to the Federal Reserve Bank of St. Louis, a reserve currency is a widely accepted currency that governments and central banks hold as part of their official foreign exchange reserves. Most of those dollars are not stacks of bills in a vault: they are held as dollar-denominated assets, especially U.S. Treasury securities.

Countries keep reserves to pay for imports, service foreign debt and have a cushion when exchange rates turn volatile. For that, they need a currency others accept without hesitation and that can be swapped quickly for other assets.

How did the dollar end up at the center?

The turning point came at the end of World War II. In July 1944, 730 delegates from 44 nations met at the Mount Washington Hotel in Bretton Woods, New Hampshire, to design the postwar monetary order. According to Federal Reserve History, the agreed rules were:

The dollar could be converted into gold at $35 an ounce.
Other countries kept their currencies fixed, but adjustable, against the dollar, within a 1 percent band.
The conference created the International Monetary Fund, which formally came into existence in December 1945, and the International Bank for Reconstruction and Development, now part of the World Bank Group.

The system lasted until 1971, when President Richard Nixon ended the dollar's convertibility into gold. Curiously, losing that anchor did not knock the dollar off its perch: it stayed dominant even without the gold link that had given it the role. The symbol that goes with it has a story of its own: where the dollar sign comes from.

How much does the world use the dollar today?

The International Monetary Fund (IMF) publishes the currency makeup of official reserves every quarter, in a dataset known as COFER. In the latest release available, published on September 30, 2026 and covering the second quarter of 2026, the dollar accounted for 56.70% of reserves, down from 57.18% the previous quarter. Other measures compiled by the Federal Reserve tell a similar story:

Measure	Dollar share	Date and source
Official foreign exchange reserves	56.70%	Q2 2026, IMF
Foreign exchange trades	about 89%	April 2025, BIS, cited by the St. Louis Fed
Foreign-currency debt issuance	about 60%	steady since 2010, Federal Reserve
International bank claims	about 55%	data through 2024, Federal Reserve

In currency trading, shares add up to 200% because every trade involves two currencies. For comparison, in the same IMF release the euro held 20.60% of reserves, the yen 4.96% and China's renminbi 2.11%. The Federal Reserve also estimates that more than $1 trillion in U.S. banknotes, roughly half of all those outstanding, was held by foreigners in the first quarter of 2025. Little wonder dollar bills are among the most closely inspected in the world; here is how to tell if money is fake.

Why did the dollar stay on top after gold?

Federal Reserve analyses point to a combination of factors rather than a single reason:

Economic size: the United States accounted for about 26% of world GDP in 2024, according to World Bank data cited by the St. Louis Fed.
Large, deep and liquid markets, with plenty of dollar assets that can be bought or sold quickly.
Stability, openness to trade and capital flows, strong property rights and the rule of law.
Trust in legal, political and financial institutions, including the government's commitment to repay its debts.

For the United States, this position has practical perks: the St. Louis Fed notes, for example, that demand for Treasuries means the government does not need to offer as high an interest rate to attract buyers.

Is the dollar's share of reserves changing?

It used to be larger. According to the Federal Reserve, the dollar peaked at 72% of official reserves in 2001 and stood at 58% in 2024. The IMF figure for the second quarter of 2026, 56.70%, remains below that peak, while the euro holds second place with roughly a fifth of the total. Quarter-to-quarter moves can reflect price changes and portfolio shifts, and the IMF noted that exchange-rate movements had only a limited effect in that period.

The numbers describe a lead that has narrowed since its high point and remains wide all the same. What happens next depends on choices made by governments, central banks and investors around the world, which no chart can settle in advance; the most reliable snapshot is simply the IMF's next quarterly release.