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What Is Interest Rate Parity And Its Formula

02 Aug 2023

What Is Interest Rate Parity?

Interest Rate Parity (IRP) is an economic theory that emphasizes the close link between the exchange rate of a currency and the interest rate. It is a critical indicator for determining the returns from investing in two distinct currencies. However, due to the difference in interest rates between the currency pairs, Interest Rate Parity may not always occur. When an international or a domestic asset is expected to depreciate or appreciate, the situation occurs. 

What Is Interest Rate Parity Formula?

While an interest rate parity calculator can be used to compute the forward exchange rate, it is essential to understand the concept by knowing the IRP formula. The Interest Rate Parity formula is as follows:



  • Ce is Current Spot Exchange
  • Fu is the Exchange Rate for Forwards
  • iA is the Country A interest rate
  • iB is the Country B interest rate

According to the IRP theory, there is a close relationship between spot rates, interest rates and future rates in the foreign currency market. The future/forward exchange rate considers the interest rates of the two nations, thus investors cannot profit from interest rate differentials. RD Calculator is a tool that can helps you calculate the maturity amount and interest on your recurring deposit.

To avoid accumulating forward premiums, the IRP forward exchange rate should not be higher than the actual forward exchange rate. A forward contract is used when an investor exchanges currency A for currency B at the spot rate and invests it at the foreign interest rate. When the forward contract expires, the investor converts currency B back to currency A. The investor obtains a forward premium if the forward exchange rate is higher than the IRP ahead exchange rate. 

When the Interest Rate Parity requirements are met, the no-arbitrage principle applies to the foreign currency market, which means that the return on investment (ROI) for both currencies is the same. The IRP, on the other hand, does not necessarily result in an equilibrium condition. 

The Interest Rate Parity formula is based on assumptions that may not hold in practice. The first is that capital is movable, and capital transfers between countries are unrestricted. The second need is that the assets, in this case, currency pairs, are completely interchangeable and have equivalent liquidity and risk. Third, the principle of non-arbitration is still valid. Finally, the foreign exchange market must be in balance. 

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What Is The Significance Of Interest Rate Parity (IRP)?

Interest Rate Parity (IRP) is a critical financial indicator in the foreign currency market that demonstrates the interdependence of the spot exchange rate, interest rate, and future exchange rate. The no-arbitrage concept safeguards the foreign currency market from severe volatility and arbitrage benefits by institutions such as banks. Furthermore, it aids in understanding the determination of exchange rates, i.e. the value of one currency versus another and how it may fluctuate owing to market developments. 

The Interest Rate Parity theory assists investors and market participants in understanding the foreign currency market and making the best possible investment decisions. It is crucial to recognize, however, that a variety of reasons and events can destabilize the market and introduce volatility into 'risk-free' assets. The actual forward exchange rate at a future date may result in instances where forward premiums are earned or losses are incurred through forward discounts. 

How Can Interest Parity Affect Currency Trading?

In currency trading, interest rate parity is a critical measure. It assists currency traders in making risk-free investments by determining the forward/future exchange rate, which ensures that the returns on assets for currency pairs remain constant. As a result, arbitrage does not cause instability in the foreign exchange market and corporations and financial institutions do not profit from it. 

Furthermore, because the conditions for IRP are not always applicable, investors can see how different interest rates can cause currency assets to depreciate or appreciate. This can assist individuals in making informed financial selections and potentially earning or avoiding losses through currency trading. 

Wrapping Up

Interest Rate Parity is a fundamental financial and economic theory that emphasizes the interdependence of the future exchange rate, spot exchange rate, and interest rates in currency trading. It adheres to the no-arbitrage principle in the foreign exchange market to prevent profiteering from pricing inefficiencies between two currencies. Simply said, the ROI for both currencies will be the same at a given point in time. 

Interest Rate Parity is based on assumptions that are difficult to maintain or reproduce in practice. External causes and risks have the potential to disrupt the foreign currency market and cancel the IRP equilibrium. 

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