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Nominal Rate, Inflation & Real Rate Calculator

Compare the exact inflation-adjusted rate with the simple nominal-rate-minus-inflation approximation.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Use the result with context

Results are estimates for planning and education. Confirm rates, taxes, fees, and legal requirements with the relevant institution or a qualified professional before making a financial decision.

Formula and method

A nominal rate of 26% with 20% inflation gives an exact real rate of 5%, since 1.26/1.20 − 1 = 0.05. The subtraction approximation gives 6%.

Exact real rate = (nominal rate − inflation) / (1 + inflation); approximation = nominal rate − inflation

Worked example

Enter these known values and leave the other values blank.

Nominal rate
26 %
Inflation rate for the same period
20 %
Exact inflation-adjusted rate
5 %
Simple subtraction approximation
6 %

Assumptions and limitations

  • Use rates for the same period. With expected inflation, the result is a modeled expected real rate; it is not a prediction of realized returns.
  • Nominal, inflation and exact real rates must exceed minus 100%, so their gross factors stay positive. Fees and taxes are excluded.
  • The subtraction approximation is closer when rates are small. The exact ratio accounts for the interaction between inflation and the nominal rate.

Common questions

Can the inflation rate be negative?

Yes, provided it exceeds minus 100%. A negative inflation input represents a falling price level over the selected period.

Can I solve for the nominal rate?

Yes. Leave the nominal rate blank and enter inflation and the exact real rate. The implied nominal factor is the real factor multiplied by the inflation factor.

References

Bookify adds explicit model-domain checks: The nominal gross return factor must be positive. The modeled price-level factor must be positive. The real gross return factor must be positive.

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