What is the difference between nominal and real interest rates?

• A. Real is observed rate; nominal adjusts for inflation.
• B. Both are identical; there is no difference.
• C. Nominal is always higher than real by policy mandate.
• D. Nominal is observed rate; real adjusts for inflation.

Answer: (D)

In interest-rate terms, you distinguish between what is quoted and what that rate actually buys you over time. The nominal rate is the rate you observe or are quoted—it’s the number schools and lenders present. The real rate strips out the effect of inflation, showing how much your purchasing power grows after rising prices are taken into account.

A handy way to think about it is: real rate ≈ nominal rate minus inflation. The exact relationship is real = (1 + nominal) / (1 + inflation) − 1, but the simple difference is a good intuition. For example, if the nominal rate is 5% and inflation is 2%, the real rate is about 3%, meaning your wealth grows in purchasing power by roughly 3% per year. If inflation is higher than the nominal rate, the real rate becomes negative, so even earning interest you’d still be losing purchasing power.

This is why the description that the nominal rate is the observed rate while the real rate accounts for inflation is the best match: it cleanly separates what you’re promised from how inflation affects what that promise is actually worth in terms of buying power.