What is Interest rate parity and its Formula

  •  5 min
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  • 05 Oct 2023
What is Interest rate parity and its Formula

Key Highlights

  • IRP is a fundamental principle in global finance, ensuring equilibrium in foreign exchange markets and guiding investors, entrepreneurs, and policymakers.

  • Forward exchange rates are agreed upon today for future transactions and are essential for international trade and finance.

  • IRP helps eliminate arbitrage opportunities in currency markets, influencing trading strategies and maintaining market efficiency.

The interest rate parity formula can be expressed as follows.

F0=S0×(1+ic / 1+ib)

Where: F0 ​ =Forward Rate S0 ​ =Spot Rate ic ​ =Interest rate in country c Ib

=Interest rate in country b

where: The forward exchange rate represents the future exchange rate at which the currency can be exchanged. However, the general exchange rate is the current exchange rate of the market. The formula shows the relationship between this rate and interest rates in the two countries.

The parity of interest means that if there is a difference between interest rates in two countries, exchange rates will change equally and oppositely in the future to eliminate the possibility of arbitrage.

The forward exchange rate is an important concept in international finance. It refers to an exchange rate that can be exchanged for another currency at a specified future date. Unlike the spot exchange rate which represents the current market value of a currency and is used for immediate transactions, forward exchange rates are currently agreed upon but used later. Understanding forward exchange rates is important for transactions, finance investors and policymakers involved in international trade and finance.

Future Date: The forward exchange rate indicates the future date of the transaction. This can last from a few days to a few months to a year. The pricing has been approved today, but the actual change takes place at a specific date in the future.

Currency pairs: Like all exchange rates, advanced exchange rates have currency pairs such as USD/EUR, which represent the value of one currency (e.g., the U.S. dollar) in another currency (e.g.). euro) in.

Agreement: The forward amount is determined by agreement between two parties, usually facilitated by financial institutions or banks. These contracts are often used to hedge exchange rate fluctuations or to estimate future cash flows.

Covered Interest Rate Parity (CIRP) and Uncovered Interest Rate Parity (UIRP) are two important concepts in international finance that describe the relationship between interest rates and exchange rates.

Covered Interest Rate Parity (CIRP) CIRP states that when investors use forward contracts to cover their foreign exchange risk, the interest rate differential between two currencies should be equal to the percentage difference between the forward exchange rate and the spot exchange rate over the same period. In simpler terms, CIRP suggests that there should be no arbitrage opportunities when interest rate differentials are balanced out by corresponding changes in the forward and spot exchange rates.

Uncovered Benefits (UIRP) However, the UIRP assumes that investors do not use forward contracts to hedge their foreign exchange risk. Instead, the UIRP implies that the expected change in the exchange rate between two currencies is equal to the difference between their nominal interest rates. In other words, if investors expect high returns from a high-interest-bearing investment in a currency, they should also expect that currency to decline in value in the future.

Equal interest rates help eliminate arbitrage opportunities in the money market. If the spread between two countries is not consistent with expected changes in exchange rates as determined by the CIRP or UIRP, traders can use these spreads to earn risk-free profits In practice, financial institutions and traders regularly monitor interest rate differentials and adjust their trading strategies to prevent arbitrage and maintain market efficiency


The interest rate parity (IRP) remains a fundamental principle of international finance, serving as the basis for understanding the complex relationship between interest rates and exchange rates This basic concept provides valuable insights for investors, entrepreneurs and policymakers participating in the global market. The equal interest rate model mathematically mirrors this principle, preventing differences between currencies and their respective interest rates

With the global economy becoming increasingly interconnected, Interest rate parity IRP stands as a guiding principle promoting equilibrium in foreign exchange markets. It emphasises the importance of interest rates in setting the value of money and emphasises that differences in the quantity of money cause proportionate changes in exchange rates

FAQs on Interest Rate Parity and its Formula

Failure to maintain a flat interest rate creates arbitrage opportunities, resulting in rapid and significant liquidity until the market corrects the anomaly.

Yes, equal interest rates can be applied to pairs of currencies at the same time. It provides a framework for understanding the relationship between currencies and interest rates.

Yes, changes in inflation can affect interest rate equity. The money supply in low-inflation countries appreciates relative to those in high-inflation countries, affecting interest rates and exchange rate equilibrium in the market.

Traders use the parity interest rate model to assess potential arbitrage opportunities, forecast currency movements, and formulate trading strategies based on interest rate differentials between currencies.

By balancing the relationship between interest rates and exchange rates, the strategy ensures that there is no risk-free opportunity for arbitrage.

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