How exchange rates actually work — and what moves them
If you've ever watched the pound buy more dollars one week and fewer the next, you've felt the effect of a floating exchange rate without necessarily seeing what's underneath it. For a business paying overseas suppliers or collecting revenue in another currency, those movements aren't abstract — they land directly on your margins. This guide explains what an exchange rate really represents, what pushes it up and down, and why the number you see quoted is rarely the number you pay.
What an exchange rate is, precisely
An exchange rate is simply the price of one currency expressed in another. When EUR/USD is quoted at 1.17, it means one euro is worth 1.17 US dollars. The first currency in the pair (EUR here) is the base; the second (USD) is the quote. The rate tells you how many units of the quote currency it takes to buy one unit of the base.
This ordering matters more than it first appears. "EUR/USD is rising" means the euro is strengthening against the dollar — the same event, described from the dollar's side, is "the dollar is weakening." For a business, the relevant question is never "is the rate going up or down" in the abstract, but "is it moving in the direction that helps or hurts my position" — which depends entirely on whether you're buying or selling each currency.
Why rates move at all
Currencies float against each other because they're traded continuously in the world's largest market — foreign exchange turns over trillions of dollars a day. Prices move for the same underlying reason any market price moves: the balance of buyers and sellers shifts. The forces behind those shifts fall into a few broad categories.
Interest rates and central bank policy. This is the single biggest driver over the medium term. When a country's central bank raises interest rates, holding that currency becomes more attractive — investors can earn more by parking money there — so demand for it rises and it tends to strengthen. Much of the day-to-day movement in major pairs is the market repricing its expectations of what central banks will do next. A rate decision that surprises the market can move a currency sharply in minutes.
Inflation. A currency that is losing purchasing power at home tends to weaken abroad over time. Persistently higher inflation in one country relative to another erodes the real value of its currency, and markets price that in.
Economic data and growth. Employment figures, GDP, manufacturing surveys, trade balances — strong data tends to support a currency because it implies a healthier economy and, often, firmer interest rates ahead. Weak data does the opposite. This is why an otherwise dull-sounding statistics release can nudge a rate.
Political stability and risk sentiment. Elections, referendums, geopolitical tension, and sudden shocks all feed into how safe investors judge a currency to be. In uncertain moments, money often flows toward currencies perceived as safe havens — historically the US dollar, the Swiss franc, and the Japanese yen — regardless of the specific economics.
Trade and capital flows. Countries that export more than they import see steady demand for their currency from foreign buyers, which is broadly supportive over the long run. Large cross-border investments and capital movements do the same in the shorter term.
No single factor operates in isolation. On any given day the rate reflects the market's continuously updated weighing of all of them at once, which is why short-term movements can look noisy even when the longer-term direction is clearer.
The rate you see versus the rate you get
Here is the part that catches most businesses out. The exchange rate quoted in the news, on Google, or in this guide is the mid-market rate — the midpoint between what buyers are bidding and what sellers are asking, at that moment, in the wholesale market. It's the truest single measure of what a currency is worth.
It is almost never the rate you'll be given when you actually convert money. Banks and brokers add a margin — a spread — to the mid-market rate, and that margin is where much of their revenue on the transaction comes from. You might see EUR/USD at 1.17 quoted everywhere, then be offered 1.15 by your bank to actually buy dollars. That gap, often invisible because it's baked into the rate rather than shown as a fee, is the real cost of the conversion.
The size of that margin varies enormously depending on your provider, your transaction size, and how much you've negotiated. On a large payment, a spread that looks like a rounding error in the fourth decimal place can amount to a meaningful sum. Understanding that the headline rate and your achievable rate are two different numbers is the first step to managing FX cost deliberately rather than accepting whatever you're handed.
What this means for a business paying or receiving in foreign currency
If you have an invoice due in a foreign currency next month, three things are true at once: the mid-market rate will move between now and then, the margin your provider charges sits on top of wherever that rate lands, and neither of those is something you control. What you can control is timing, provider choice, and how much attention you pay to the difference between the quoted rate and the real one.
None of this is a prediction, and none of it is advice about when to convert — rates are genuinely unpredictable in the short term, and anyone claiming otherwise is guessing. But understanding the mechanics turns a currency movement from something that happens to your business into something you can at least see clearly and plan around.
The short version
An exchange rate is the price of one currency in another, set continuously by a global market. It moves mainly on interest rates, inflation, economic data, and risk sentiment. The rate you read about is the mid-market rate — the wholesale midpoint — and the rate you actually receive is that number minus a margin your provider builds in. Knowing the difference between the two is worth more to most businesses than trying to forecast where the rate goes next.
