Real Rate of Return Calculator (Fisher Effect)
Measure the true purchasing power expansion of your investments after accounting for inflation. This calculator applies the exact Irving Fisher Equation rather than flawed linear subtraction, showing your true real economic growth.
Headline paper return quoted by your broker or bank account
Consumer price index (CPI) annual inflation rate
Portfolio principal amount to model purchasing power gain
Purchasing power growth rate calculated via exact Fisher Equation
How to Use This Calculator
- Enter your gross nominal investment return percentage.
- Enter the prevailing annual CPI inflation rate.
- Input your invested capital balance to view monetary purchasing power changes.
- Review the exact real return percentage and nominal inflation drag.
Formula & Calculation Methodology
Formulated by economist Irving Fisher, the exact equation models how price levels dilute the future nominal value of money. Linear subtraction (Nominal - Inflation) consistently overstates real yield.
Worked Example
Stock portfolio yielding 9.0% nominal return during 3.5% inflation on $50,000 capital
Frequently Asked Questions
Why is the exact Fisher equation better than subtracting inflation?↓
The simple subtraction rule (9% - 3.5% = 5.5%) assumes inflation only erodes principal. In reality, inflation also diminishes the purchasing power of your investment gains, making the true return 5.31%.
Can real rate of return be negative?↓
Yes. If a high-yield savings account earns 4% while inflation runs at 6%, your real return is -1.89%, meaning your savings lose purchasing power each year despite nominal dollar growth.
What is the historical real return of the US stock market?↓
Over the last century, the S&P 500 has delivered approximately 10% nominal compound annual returns. After subtracting historical ~3% inflation, the average real return is approximately 6.8%–7.0%.
How does taxation affect the real rate of return?↓
Taxes are assessed on nominal gains, not real gains. When inflation is high, taxation can turn modest positive real returns into negative after-tax real returns.
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Open calculator →Source Citation & Disclaimer
Informational tool only; not licensed tax, legal, or financial advice.