# Real Interest Rate Calculator

URL: https://speedycalculator.com/calculators/finance/real-interest-rate/
Last updated: 2026-10-25

> The real interest rate calculator works out the inflation-adjusted interest rate – exactly and approximately – and the real after-tax return on savings or the real cost of a loan.

## Inputs

- Nominal interest rate (%)
- Inflation rate (%)
- Tax rate on interest (%)

## Results

- Real interest rate
- Approximation (nominal − inflation)
- Real after-tax rate

## Formula

```
Real rate = (1 + nominal) ÷ (1 + inflation) − 1
After-tax real rate = (1 + nominal × (1 − tax)) ÷ (1 + inflation) − 1
```

## Explanation

When inflation exceeds the interest rate, savers lose buying power – real rates were deeply negative in 2021–22. For borrowers, high inflation reduces the real cost of fixed-rate debt.

### How to use the Real Interest Rate Calculator

- **Nominal interest rate**
- **Inflation rate**
- **Tax rate on interest**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter the nominal interest rate, inflation and your tax rate on interest.

### Tips

- Use real (inflation-adjusted) figures to compare across years.
- Check whether data are seasonally adjusted.
- Use the same currency and base year throughout.
- Economic models simplify reality – treat results as illustrations, not forecasts.

### Common mistakes to avoid

- Mixing nominal and real values.
- Comparing percentage changes with percentage-point changes.
- Treating correlations as causes.

### Inputs explained

FieldWhat to enterNominal interest rateIn %Inflation rateIn %Tax rate on interestIn %

### What each result means

- **Real interest rate** = ((1 + [Nominal interest rate]÷100)÷(1 + [Inflation rate]÷100) - 1)×100
- **Approximation (nominal − inflation)** = [Nominal interest rate] - [Inflation rate]
- **Real after-tax rate** = ((1 + [Nominal interest rate]÷100×(1 - [Tax rate on interest]÷100))÷(1 + [Inflation rate]÷100) - 1)×100

### Example values

How the main result changes when **Nominal interest rate** changes and everything else stays at the example values above:

Nominal interest rate (%)Real interest rate (%)2.25-0.7283.380.3644.51.4565.632.5496.753.64195.825

## Worked example

Inputs — Nominal interest rate: 4.5 %; Inflation rate: 3 %; Tax rate on interest: 22 %.

Results — **Real interest rate = 1.456 %**; Approximation (nominal − inflation) = 1.5 %; Real after-tax rate = 0.495 %.

## FAQ

**What is the real interest rate?**
The interest rate after removing inflation.

**Can the real interest rate be negative?**
Yes – when inflation is higher than the nominal rate.

**Why does the after-tax real rate matter?**
Taxes apply to the nominal interest, reducing real returns further.

**What formula does the Real Interest Rate Calculator use?**
Real rate = (1 + nominal) ÷ (1 + inflation) − 1.