The US dollar is issued by the Federal Reserve System: the Board is the issuing authority for Federal Reserve notes and places the annual order with the Treasury’s Bureau of Engraving and Printing, which prints them. The euro is issued by the Eurosystem — under Article 128(1) of the Treaty on the Functioning of the European Union the European Central Bank holds the exclusive right to authorise the issue of euro banknotes, and the ECB and the national central banks issue them. The ECB states that euro banknotes and coins are legal tender in 21 of the 27 EU Member States, and that cash payments are made in the same currency by about 358 million people. In ISO 4217 the dollar is USD, numeric 840, and the euro is EUR, numeric 978; both carry two minor units, so both settle to the cent.

USD/EUR is the most traded currency pair in the world. In the BIS Triennial Central Bank Survey for April 2025 it accounted for 21.2% of global OTC foreign exchange turnover, out of $9.6 trillion a day. Underneath the trading sits real commerce: the US Census Bureau recorded 2025 US goods exports to the EU of $412.5 billion against imports of $632.9 billion, and Eurostat reported the United States as the EU’s largest services partner in 2024, with EU services exports of €344 billion and imports of €483 billion. People move too — the US National Travel and Tourism Office recorded Western Europe as the largest source region of visitors to the United States in 2024, at 13.07 million arrivals.

Neither central bank sets this rate. The ECB states its main aim is to maintain price stability; the Federal Reserve’s statutory goals are maximum employment, stable prices and moderate long-term interest rates. The exchange rate is a by-product. The ECB describes the channel plainly: policy that compresses the return on domestic bonds encourages investors to rebalance portfolios towards foreign, higher-yielding assets, and exchange rates adjust to clear the resulting cross-border capital flows. The Federal Reserve describes the mirror image — changes in US interest rates alter the relative attractiveness of US versus foreign bonds. Trade and investment flows supply the rest of the demand on each side. That is the wiring; it says nothing about direction.

A published reference rate is not a dealing rate. The ECB says its euro reference rates are "published for information purposes only" and that "using the rates for transaction purposes is strongly discouraged". The gap between that benchmark and what a customer is quoted is a real cost, and EU law treats it as one: since 19 April 2020, Regulation (EU) 2019/518 has required currency conversion charges at ATMs and at the point of sale to be expressed as a percentage mark-up over the ECB’s latest euro reference rates, so that the margin can be compared across providers. Foreign exchange also has a weekend. CLSSettlement, which settles the most actively traded currencies, operates 5.5 days a week — closing 02:00 CET on Saturday and reopening 22:00 CET on Sunday — so a Saturday and a Sunday contain no market prices to record.