Nominal Interest Rate: Formula, What It Is vs. Real Interest Rate


Discover the intricacies of nominal interest rates in our comprehensive guide. Explore the divergence between nominal and real interest rates and their impact on your financial choices.

What is nominal interest rate?

Nominal interest rate, often known as the “nominal rate,” holds a pivotal place in finance. This rate signifies the interest accrued or charged on a loan or investment before factoring in inflation. Essentially, it represents the unadjusted interest rate, failing to account for the evolving value of money over time. Additionally, “nominal” can describe the publicly stated interest rate on a loan, excluding compounding of interest and any associated fees.

Understanding the contrast: nominal vs. real interest rates

To truly grasp the significance of nominal interest rates, one must differentiate them from real interest rates. Nominal rates, unaffected by inflation, lay the groundwork for various interest rates established by financial institutions. In contrast, real interest rates incorporate the influence of inflation, rendering a more precise reflection of an investment’s genuine growth or the true cost of a debt over time.

The formula connecting nominal and real interest rates is simple: nominal rate = real interest rate + inflation rate. Prudent financial decision-making often involves prioritizing the real interest rate to ensure investments maintain their value amidst the erosive impact of inflation.


Here are the pros and cons of nominal and real interest rates.

  • Nominal interest rates provide a clear baseline for financial calculations.
  • They help establish various interest rates used by financial institutions.
  • Nominal rates can be useful for short-term assessments and quick comparisons.
  • Nominal rates don’t consider the impact of inflation, leading to inaccurate long-term predictions.
  • They may not reflect the actual cost or growth of investments over time.
  • Reliance on nominal rates alone can result in financial decisions that overlook the effects of inflation.

Role of central banks and the federal funds rate

Central banks play a pivotal role in determining short-term nominal interest rates, forming the foundation for various borrowing and lending rates offered by financial institutions. Following significant economic downturns, central banks might maintain artificially low nominal rates to invigorate economic activity through low real interest rates, encouraging borrowing and spending among consumers.

Conversely, during inflationary phases, central banks often elevate nominal rates to counterbalance escalating prices. However, inaccurately gauging inflation levels and sustaining excessively high nominal rates can lead to economic stagnation due to decreased consumer spending.

Impact of compounding and effective interest rates

While the nominal rate represents the publicly stated interest on a loan, the effective interest rate integrates both compounding and associated fees. Borrowers and investors focus more closely on the effective rate since it accurately mirrors the actual cost or earnings they’ll experience. The annual percentage yield (APY) exemplifies an effective interest rate, accounting for both compounding and fees.

Calculating the nominal interest rate (n) for a specific period when the effective rate is known involves the formula:

n = m × [ ( 1 + e)^(1/m) – 1 ]

Where e = effective rate and m = number of compounding periods.

On the other hand, borrowers typically favor the effective rate over the nominal rate. The formula for the effective interest rate (e) based on the nominal rate is:

e = (1 + n/m)^m – 1

Where n = nominal rate and m = number of compounding periods.

Frequently asked questions

How do nominal interest rates differ from real interest rates?

Nominal rates disregard inflation, while real rates encompass it, offering insight into an investment’s actual growth or a debt’s authentic cost.

Why do investors prioritize real interest rates?

To safeguard against the erosion of purchasing power due to inflation, investors prioritize the real interest rate. By considering the real rate, investors ensure their returns outpace inflation, preserving the actual value of their investments. A method to gauge the real rate in the United States is by observing the interest rates of Treasury Inflation-Protected Securities (TIPS). The gap between Treasury bond yields and TIPS yields provides insights into inflation expectations.

What sets the nominal rate apart from APY?

APY (annual percentage yield) represents the effective interest rate, accounting for compounding and fees, often surpassing the nominal rate’s relevance.

How can the effective rate be calculated if the nominal rate is known?

The effective rate, factoring in compounding, can be computed using the nominal rate. The formula is: e = (1 + n/m)^m – 1 (where n = nominal rate and m = compounding periods).

What other sources provide insights into real interest rates?

Another source for estimating real rates in the United States is the yield gap between Treasury bonds and Treasury Inflation-Protected Securities (TIPS), revealing inflation expectations.

Key takeaways

  • Nominal interest rates operate without factoring in inflation.
  • Real interest rates consider inflation, providing a more accurate financial picture.
  • Central banks influence nominal rates, affecting borrowing and lending rates.
  • Effective interest rates incorporate compounding and fees for a more precise cost estimation.
  • Investors prioritize real interest rates to protect against purchasing power erosion caused by inflation.
View article sources
  1. Monetary Policy Space in a Recession: Some Simple Interest Rate Arithmetic – Federal Reserve
  2. Nominal Interest Rates On Special Issues – Social Security Administration
  3. Nominal, Period, and Effective Interest Rates – Pennsylvania State University
  4. How To Lower The Interest Rate On My Student Loans – SuperMoney
  5. Understanding Purchasing Power and the Consumer Price Index – SuperMoney