Nominal returns tell you how much your money grew in dollar terms, but real returns tell you how much your purchasing power actually increased. Inflation silently erodes the value of investment gains, which means a 10% nominal return with 3.5% inflation does not actually grow your wealth by 10%. Understanding this distinction is critical for long-term financial planning.

The Fisher equation calculates the real return: Real Return = (1 + Nominal Return) / (1 + Inflation Rate) - 1. This is more accurate than the simplified approximation of simply subtracting inflation from nominal return, especially when rates are large. The Fisher equation properly accounts for the compounding interaction between returns and inflation.

For example, with a 10% nominal return and 3.5% inflation, the real return is (1.10 / 1.035) - 1 = 6.28%, not the 6.5% you get from simple subtraction. On a $100,000 investment over 10 years, the nominal value grows to $259,374, but in today's purchasing power it is worth only $183,846. The difference of $75,528 represents the value eroded by inflation over the decade.