Real Interest Rate Calculator

Macroeconomics
Updated Apr 2026 • Has calculator

The nominal interest rate adjusted for inflation using the Fisher equation.

Calculate Real Interest Rate

Nominal rate, e.g. Fed Funds Rate or bond yield

Annual CPI inflation rate

Real Interest Rate

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Not investment advice.

What is Real Interest Rate?

The real interest rate strips out the effect of inflation from a nominal interest rate, revealing the true purchasing-power return on an investment or the true cost of borrowing. The precise calculation uses the Fisher equation: divide (1 + nominal rate) by (1 + inflation rate) and subtract one. When inflation is low, the approximation (nominal − inflation) is accurate enough; when both rates are high, only the Fisher equation gives the correct answer. Central banks focus intensely on real rates: a real rate below zero means savers are losing purchasing power even while earning a positive nominal return.

Formula

Real Rate = (1 + r_nom) ÷ (1 + r_inf) − 1

Worked Example

Worked example — US Federal Reserve / BLS — 2024

Q1 2024

Step 1  Fed Funds Rate (nominal): 5.33%
Step 2  US CPI inflation (YoY): 3.4% (BLS, March 2024)
Step 3  Real Rate = (1.0533 / 1.034) − 1 = 1.01867 − 1 = 1.87%
Step 4  → Despite a nominal rate of 5.33%, investors earn only ~1.87% in real purchasing-power terms

Source: FRED — Federal Funds Effective Rate & CPI (2024-03-31)

How to Interpret Real Interest Rate

< 0
Negative Real Rate — inflation exceeds nominal; savers lose purchasing power
0 – 2
Low Positive (0–2%) — accommodative monetary policy
2 – 4
Neutral (2–4%) — typical long-run equilibrium range
> 4
High Real Rate (>4%) — restrictive; discourages borrowing and investment
Sources
  1. FRED — Federal Funds Effective Rate
  2. BLS — Consumer Price Index
  3. Investopedia — Real Interest Rate