The real exchange rate is the nominal exchange rate between two currencies adjusted for the difference in price levels between the two countries. It tells you what a unit of one country’s money actually buys in another, rather than just how it converts on a currency board. A country whose real exchange rate rises watches its exports grow more expensive abroad; a country whose real rate falls sees its goods become a bargain on the world market.
Nominal vs. Real
The nominal exchange rate is the raw market price of one currency in another. If the dollar-to-euro rate is 1.10, each dollar buys 1.10 euros. That number moves constantly, but it says nothing about what those euros can purchase once you have them.
The real rate fills that gap. It adjusts the nominal rate for the price-level difference between two countries, producing a figure that reflects genuine purchasing power. If U.S. inflation runs well above the euro area’s while the nominal rate holds flat, American goods have effectively become more expensive relative to European goods. The real exchange rate captures that shift even when the number on the currency board hasn’t budged.1International Monetary Fund. Real Exchange Rates: What Money Can Buy
Two countries can hold a stable nominal rate for years while their real rate drifts sharply because of diverging inflation paths. Anyone watching only the nominal number would miss that the competitive picture between them has changed.
The Formula
The standard formula is compact:
Real Exchange Rate (RER) = e × (P* ÷ P)
The variable e is the nominal exchange rate expressed as units of domestic currency per unit of foreign currency (for example, dollars per euro). P* is the price level in the foreign country, and P is the price level at home.1International Monetary Fund. Real Exchange Rates: What Money Can Buy Multiplying the nominal rate by the ratio of the two price levels produces a single number that accounts for both currency conversion and purchasing power.2Federal Reserve Bank of St. Louis. Constructing a Bilateral Real Exchange Rate
A Worked Example
Say one euro costs $1.10, a representative basket of goods runs €100 in Europe, and the same basket costs $120 in the United States. The real exchange rate is 1.10 × (100 ÷ 120) = 0.92. The European basket costs about 92 percent of what the American basket costs once you factor in both the exchange rate and local prices. European goods are the better deal, and American exporters sit at a price disadvantage.
When inflation rises faster at home than abroad and the nominal rate doesn’t adjust to compensate, P climbs relative to P*, the ratio shrinks, and the real exchange rate falls. Your currency may look stronger on paper, but exporters lose ground.
Where the Price Data Comes From
Plugging numbers into the formula requires reliable price-level data for both countries. The most common proxy is the Consumer Price Index, which tracks the cost of a standard basket of household goods and services. In the United States, the Bureau of Labor Statistics publishes CPI covering all goods and services purchased by urban households, with index data available nationally and for 23 local areas.3U.S. Bureau of Labor Statistics. Consumer Price Indexes Overview
CPI is not always the right choice. Some economists prefer the Producer Price Index for trade-competitiveness work. CPI includes import prices but leaves out exports, while PPI does the opposite: it captures export prices but excludes imports.4Federal Reserve Bank of St. Louis. The Differences Among Price Indexes If the question is how competitive a country’s producers are against foreign rivals, PPI gives a cleaner picture because it reflects what producers charge rather than what consumers pay after retail markups and imported goods enter the mix.
Nominal exchange rates and price index series for dozens of countries are available through the Federal Reserve Economic Data (FRED) system maintained by the Federal Reserve Bank of St. Louis.2Federal Reserve Bank of St. Louis. Constructing a Bilateral Real Exchange Rate FRED lets you pull historical CPI and PPI data across major trading partners, which is a practical starting point for building your own comparison.
Purchasing Power Parity
Purchasing Power Parity is the theoretical anchor behind real exchange rate analysis. The idea is that identical goods should cost the same in different countries once converted to a common currency. If a pair of running shoes costs $100 in New York, PPP says it should cost the equivalent of $100 in Tokyo after converting yen. When prices diverge from that benchmark, the real exchange rate signals that one currency is overvalued or undervalued relative to the other.1International Monetary Fund. Real Exchange Rates: What Money Can Buy
PPP never holds perfectly. Shipping costs, tariffs, taxes, and local regulations create persistent price gaps. Over long stretches, though, exchange rates tend to drift toward PPP levels, which is why economists treat it as a gravitational pull for judging fair value.
The most familiar casual test is The Economist’s Big Mac Index, published since 1986. The logic is simple: because McDonald’s sells a nearly identical burger worldwide, comparing Big Mac prices reveals an implied exchange rate. If a Big Mac costs $5.50 in the United States and the local-currency equivalent of $3.30 elsewhere, that currency looks roughly 40 percent undervalued against the dollar. The index was never meant as a precise forecasting tool, but it makes the theory tangible.
Why Rich Countries Look Structurally Expensive
Travelers to wealthy nations notice that haircuts, restaurant meals, and taxi rides cost more than in developing countries even after currency conversion. The Balassa-Samuelson effect explains why: richer countries tend to have structurally higher real exchange rates.
The mechanism runs through productivity gaps between two parts of an economy. In wealthy countries, factories and technology firms (the tradable sector) are highly productive, which lifts wages across the board. Workers in non-tradable sectors like restaurants, healthcare, and personal services command similar pay even though their productivity has not risen as sharply. Because those services can’t be imported from cheaper countries, their prices stay elevated. The overall price level ends up higher, and the real exchange rate stronger.
This matters when reading PPP data. When the Big Mac Index shows a developing-country currency as deeply undervalued, part of the gap reflects a genuine structural productivity difference rather than a distortion that markets will eventually close.
The Real Effective Exchange Rate
The formula above computes a bilateral real exchange rate between two specific countries. Most economies trade with dozens of partners at once. The Real Effective Exchange Rate, or REER, averages a country’s bilateral real rates with its major trading partners, weighted by how much trade each partner represents.1International Monetary Fund. Real Exchange Rates: What Money Can Buy
The Bank for International Settlements publishes REER indices for 64 economies, with weights derived from manufacturing trade flows that capture both direct bilateral trade and third-market competition. Weights are updated on a three-year rolling basis, so a country that redirects exports toward faster-growing markets sees its REER shift accordingly.5Bank for International Settlements. Effective Exchange Rates – Overview
A subtlety worth knowing: a country’s headline REER can look balanced even when the currency is overvalued against some partners and undervalued against others. The averaging smooths out bilateral misalignments, and policymakers watching competitiveness at a granular level still need to look at the bilateral rates underneath.1International Monetary Fund. Real Exchange Rates: What Money Can Buy
How Real Exchange Rate Movements Affect Trade
When a country’s real exchange rate appreciates, its goods become more expensive for foreign buyers. Exporters lose competitiveness, and overseas customers start shopping elsewhere. Imports become cheaper for domestic consumers, tilting spending away from locally produced goods.
Real depreciation reverses the picture. Domestic products become a better deal for foreign buyers, boosting export volumes. Imported goods get pricier at home, pushing consumers toward domestic alternatives.
The adjustment is not instant. After a real depreciation, the trade balance often worsens before it improves, a pattern economists call the J-curve effect. Import and export contracts signed at old prices take months to roll off, so a country keeps paying elevated import bills while cheaper export prices have not yet drawn enough new buyers. The typical lag runs one to two years. Countries that reverse course during the initial dip never see the competitive gains the depreciation was meant to deliver.
Persistent shifts in the terms of trade add another layer. An oil-exporting country that enjoys a sustained rise in crude prices sees its real exchange rate appreciate as foreign currency flows in, making its non-oil exports less competitive.1International Monetary Fund. Real Exchange Rates: What Money Can Buy The real rate captures that structural shift in a way the nominal rate alone cannot.
What This Means for Investors Holding Foreign Assets
Real exchange rate movements affect returns on foreign investments even when the underlying asset performs well in local-currency terms. If you hold shares in a European company and the euro depreciates 10 percent against the dollar over the year, your returns shrink by roughly that amount once converted back to dollars, regardless of how the stock did on its home exchange.
American Depositary Receipts make the risk concrete. ADRs trade in dollars on U.S. exchanges, but the underlying company earns revenue and pays dividends in a foreign currency. An unexpected depreciation of that currency drags ADR prices down as the market reprices the dollar value of foreign earnings. The effect is purely a currency translation issue, separate from anything happening with the business itself.
Institutional investors manage this exposure through currency hedging. The most common tool is a forward contract, an agreement today to sell foreign currency at a fixed rate on a future date, locking in the exchange rate and removing the uncertainty. Currency options and swaps play similar roles. Common hedge ratios among large investors are 0, 50, or 100 percent of foreign currency exposure, depending on risk tolerance and market outlook.6International Monetary Fund. Currency Hedging for International Portfolios Hedging is especially useful for bond portfolios, where currency volatility routinely dwarfs the volatility of the bonds themselves.