Real Return Calculator Formula

Understand the math behind the real return calculator. Each variable explained with a worked example.

Use the Real Return Calculator

Formulas Used

Real Return Rate

real_return = ((1 + nominal_return / 100) / (1 + inflation_rate / 100) - 1) * 100

Nominal Future Value

nominal_value = initial_amount * pow(1 + nominal_return / 100, years)

Real Future Value (Today's $)

real_value = initial_amount * pow((1 + nominal_return / 100) / (1 + inflation_rate / 100), years)

Purchasing Power Loss

purchasing_power_loss = initial_amount * pow(1 + nominal_return / 100, years) - initial_amount * pow((1 + nominal_return / 100) / (1 + inflation_rate / 100), years)

Variables

VariableDescriptionDefault
nominal_returnNominal Return(%)10
inflation_rateInflation Rate(%)3
initial_amountInvestment Amount(USD)10000
yearsTime Period(years)10

How It Works

Real vs Nominal Returns

The Fisher Equation

Real Return = [(1 + Nominal) / (1 + Inflation)] - 1

This is more accurate than simply subtracting inflation from the nominal return.

Why Real Returns Matter

Nominal returns tell you how much your money grows. Real returns tell you how much your purchasing power grows. If investments grow 10% but prices rise 3%, your actual wealth gain is about 6.8%.

Historical Real Returns

AssetNominalReal US Stocks~10%~7% US Bonds~5%~2% Cash/Savings~3%~0%

Worked Example

10% nominal return, 3% inflation, $10,000 over 10 years.

nominal_return = 10inflation_rate = 3initial_amount = 10000years = 10
  1. 01Real return = (1.10 / 1.03) - 1 = 6.80%
  2. 02Nominal value = $10,000 x (1.10)^10 = $25,937
  3. 03Real value = $10,000 x (1.068)^10 = $19,307
  4. 04Purchasing power loss = $25,937 - $19,307 = $6,630

Frequently Asked Questions

Why not just subtract inflation from the return?

Simple subtraction (10% - 3% = 7%) is an approximation. The Fisher equation (1.10 / 1.03 - 1 = 6.80%) accounts for the compounding interaction between returns and inflation and is more precise.

What inflation rate should I use?

For US planning, 2-3% is a reasonable long-term assumption based on the Federal Reserve target. For recent years, check actual CPI data. Some use 4-5% for healthcare-heavy expenses.

Can real returns be negative?

Yes. If inflation exceeds your nominal return, your purchasing power declines even though your account balance grows. This commonly happens with savings accounts and bonds during high-inflation periods.

Learn More

Guide

Inflation Impact on Savings

Understand how inflation erodes your savings and purchasing power over time. Learn strategies to protect your money, calculate real returns, and invest to outpace inflation.

Ready to run the numbers?

Open Real Return Calculator