Fundamentals

Exchange rate: what it is, how it is formed, and why it matters

By Daniel Sardá · Published on June 06, 2026

6 min read1,214 words

An exchange rate is the price of one currency expressed in another. Understanding how it is formed helps explain its movements and everyday effects.

The exchange rate is the price of one currency expressed in another. It tells us how many units of one currency are needed to buy one unit of another, so it always describes a relationship between two currencies.

If it takes 20 units of currency A to buy one unit of currency B, the exchange rate is 20 A per B. If it later takes 22, currency A has lost value relative to B. That convention matters: a rise or fall can only be interpreted correctly when we know which currency is in the numerator and which is in the denominator.

Key idea: the exchange rate does not measure the absolute value of a currency. It shows its relative value against another currency at a given moment.

How the exchange rate is formed

In a floating foreign exchange market, the exchange rate emerges from supply and demand for currencies. Individuals, companies, banks, and investors offer one currency and demand another to buy goods, invest, save, pay debts, or make international transfers.

That supply and demand changes constantly. Greater demand for exports can raise demand for the seller country's currency. A company importing machinery, by contrast, needs to acquire foreign currency to pay for it. Capital flows, interest rates, expectations, and perceptions about monetary stability also matter.

There is no single explanation for every movement. An exchange rate may change because trade changed, because investors revised their expectations, or because monetary policy altered the incentives to hold a currency. Often, several causes act at the same time.

As with other free prices that transmit information, the exchange rate condenses dispersed decisions. A change signals that the relative willingness of people to buy, sell, or hold the currencies involved has changed. The signal may be imperfect, but it is not an isolated number detached from the economic decisions that produce it.

Appreciation, depreciation, and devaluation

A currency appreciates when it gains value against another currency under a floating regime. It depreciates when it loses value as a result of market movements. The direction must always be stated against a specific currency: saying that a currency “went up” without saying against which one can be misleading.

Devaluation is different from depreciation. Devaluation is the official adjustment that reduces the value of a currency within a fixed exchange-rate regime. Depreciation, by contrast, describes a fall determined by the market under floating conditions. Both imply a relative loss of value, but they do not occur through the same mechanism.

Nominal and real exchange rates

The nominal exchange rate is the figure that usually appears in banks, exchange houses, and financial apps. It says how many units of one currency are exchanged for another. It is useful for converting prices and making payments, but it does not by itself show how much can be bought in each country.

The real exchange rate adjusts that nominal relationship for relative price levels. Its purpose is to approximate the comparative purchasing power of the currencies.

Imagine that the same basket of goods costs 100 units in one country and, after converting currencies, 130 units in another. That price difference contains information that the nominal rate alone does not capture. The real rate combines both elements: the exchange between currencies and the prices of goods and services.

This distinction helps avoid a hasty conclusion. A stable nominal rate does not necessarily mean that relative purchasing power is also stable. If prices rise at different speeds, the real rate can change even if the quoted nominal rate does not move.

Exchange-rate regimes: fixed, floating, and managed

An exchange-rate regime sets how the exchange rate is determined and what role the monetary authority plays. The three basic models are:

• Fixed: the authority maintains a parity or reference against another currency or basket of currencies. To sustain it, it needs to intervene and apply policies consistent with that goal.
• Floating: supply and demand mainly determine the price. The quote can adjust more frequently to new information.
• Managed: the market participates in price formation, but the authority intervenes at its discretion to influence certain movements, without necessarily maintaining a predetermined path.

In practice, regimes form a spectrum and may function differently from their official label. A fixed rate can reduce observed variation as long as it is sustainable, but it does not eliminate economic pressure or the risk of a future adjustment. Floating allows more visible adjustments, although it does not guarantee automatic stability either.

For that reason, no regime is universally superior in every circumstance. Its performance depends on institutions, the credibility of monetary policy, fiscal discipline, and the ability to meet the announced rules. Economic interventionism can temporarily alter a quotation, but it does not make foreign-currency scarcity or the incentives behind it disappear.

Why it matters in everyday life

The exchange rate becomes obvious when traveling or buying from a foreign store, but its effects are broader. It also influences business costs, domestic prices, savings, and trade.

When the local currency weakens, imports tend to become more expensive in local currency. This can affect final goods as well as inputs, equipment, or services used to produce within the country. The effect on domestic prices is not automatic or identical in every case: it depends on contracts, competition, margins, and how much of the exchange-rate cost is passed on to consumers.

A weaker currency can also improve the price competitiveness of some exports, because those products become relatively cheaper for foreign buyers. However, it does not guarantee higher sales: demand, production capacity, and the use of imported inputs can change the result.

For a person, the exchange rate changes the cost of travel, studying abroad, sending money, or holding savings in different currencies. For a company, it can alter revenues, debts, and costs. That is why many decisions require thinking not only about the current quote, but also about exposure to possible changes.

Common mistakes when interpreting the exchange rate

The first mistake is to treat it as a complete rating of the economy. An appreciation does not by itself prove that everything is going well, and a depreciation does not by itself prove the opposite. The exchange rate is a relative price influenced by many variables.

The second is to assume that a cheap currency always benefits exporters or that an expensive currency always benefits consumers. The effects depend on how people and firms produce, sell, buy, and finance themselves.

The third is to believe that an authority can set any exchange rate indefinitely without costs. Maintaining a parity requires resources, credibility, and coherent policies. If the official price no longer reflects economic conditions, the pressure does not disappear: it can show up as shortages, later adjustments, or other mechanisms.

A relative price that transmits information

Understanding the exchange rate requires looking beyond the figure published every day. It is a price between two currencies, a signal about decisions and expectations, and a channel through which monetary and trade changes reach households and firms.

The useful question is not only whether a currency rose or fell. It is also worth asking against which currency, under what regime, for what reasons, and with what possible effects. Those questions turn an isolated quotation into understandable economic information.