Exchange rates explained: what moves a currency, and strong vs weak effects

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If you have ever changed money for a trip, bought something from an overseas website or wondered why the news reports that the currency has hit a multi-year low, you have run into exchange rates. Here is how they work and why they matter. This guide is educational and is not advice on trading currencies.

What an exchange rate is

An exchange rate is the price of one currency in terms of another. If one US dollar buys a certain number of Korean won, that is the dollar-won exchange rate. When a currency can buy more of another currency than before, it has strengthened or appreciated; when it buys less, it has weakened or depreciated. Most major currencies are floating: their value is set by buying and selling in the foreign exchange market. Some countries peg their currency to another, usually the US dollar, or manage it within a range. Many floating currencies still see occasional intervention from their central bank.

What moves a currency

Like any price, an exchange rate reflects supply and demand. People need a currency to buy that country's goods, services and assets. Things that commonly affect demand include:

Interest rates: higher rates can attract foreign savers and investors seeking a better return, which tends to strengthen a currency. Expectations of future rate changes often matter as much as current rates.
Inflation: high inflation erodes a currency's purchasing power, and over time tends to weaken it.
Economic growth and prospects: a strong economy attracts investment.
Trade: a country that sells a lot abroad sees steady demand for its currency from foreign buyers, though the link is not always straightforward.
Risk and confidence: in times of global stress, investors often move money into currencies seen as safe havens, and out of those seen as riskier.
Politics and policy: elections, government budgets and uncertainty can all move a currency.
Commodity prices: currencies of big commodity exporters often move with the prices of what they sell.

Short-term moves are notoriously hard to predict, even for professionals, because so many factors and expectations interact.

What a strong currency means

When your currency is strong:

Travel abroad is cheaper: your money goes further on hotels, meals and shopping.
Imports are cheaper, which can help keep inflation down and lowers costs for businesses that buy materials from abroad.
Exporters struggle: their goods become more expensive for foreign buyers, which can hurt sales, profits and jobs in exporting industries.
Tourism into the country may fall, as it becomes pricier for visitors.

What a weak currency means

When your currency is weak:

Holidays abroad cost more, and so does anything priced in foreign currency, including overseas online shopping.
Imports become more expensive, which can push up prices of fuel, food and other imported goods, adding to inflation.
Exporters gain: their goods are cheaper abroad, which can boost sales and support jobs.
Inbound tourism often rises, as the country becomes better value for visitors.
Foreign-currency debts become harder to repay for anyone who earns in the local currency.

Neither is simply good or bad. A strong currency helps consumers and importers; a weak one helps exporters and the tourism industry. Which matters more depends on the economy's structure.

Tips for travellers and online shoppers

Compare the rate you are offered with the mid-market rate shown on financial news sites; the gap, plus any fees, is the real cost.
Airport exchange desks often offer less favourable rates than other options.
When paying by card abroad, you may be asked whether to pay in your home currency. This is called dynamic currency conversion, and it often comes with a worse rate than letting your card provider convert. Check your card's terms.
Check whether your card charges foreign transaction fees.

Why central banks care

A sharp fall in a currency can push up inflation through import prices, while a rapid rise can hurt exporters. Central banks watch exchange rates closely and take them into account when setting interest rates, even if they do not target a specific level. Rates change by the minute, so check a reliable live source before any exchange. Have a question about why a currency moved, or a tip for getting a good rate abroad? Share it in the comments below.