There is no point reaching for a calculator that cannot show its working. This one starts from expected inflation rate and nominal interest rate and reports approximated real interest rate and real interest rate, so you can see how each answer follows from the numbers you entered.
What Is the Fisher Equation Calculator?
The fisher equation calculator takes expected inflation rate and nominal interest rate and turns them into approximated real interest rate and real interest rate.
It is the kind of calculation you would otherwise do on the back of an envelope: mechanical, repeatable and easy to get subtly wrong without noticing.
How the Fisher Equation Figure Is Built
Each result is calculated from the ones before it, so the working is fully visible. That matters when the answer is going to be quoted to somebody else and you need to be able to explain where it came from.
The figures are exactly as good as the assumptions underneath them. Check the rates, the periods and the tax treatment before you rely on the result.
Reading the Result Sensibly
A small change in an input can move the result by much more than you would expect, particularly where the calculation divides by one of the figures you supplied. That is worth understanding before you rely on a figure.
For anything that will be committed to, write the inputs down beside the result. A number you can reproduce is worth far more than one you cannot explain.
A Worked Example
Working through an example, with expected inflation rate set to 10, nominal interest rate set to 5, the calculator returns real interest rate of -0.45455, and approximated real interest rate of -5. Substitute your own figures and the same steps produce the same kind of answer.
Frequently Asked Questions
What do I need to work out approximated real interest rate?
Enter expected inflation rate and nominal interest rate. The calculator then works through the relationship and reports approximated real interest rate and real interest rate.
What does the fisher equation actually calculate?
It takes expected inflation rate and nominal interest rate and converts them into approximated real interest rate and real interest rate using the standard relationship for this problem. Each step is applied in turn, so every output is traceable back to the numbers you typed in.
How should I enter expected inflation rate?
Use the value you actually have, in the unit shown next to the field. Enter every value in the same unit system. The calculator assumes the figures you supply are consistent, so it cannot correct a mistake that happens before the calculation starts.
Why does a small change in one value move the answer so much?
That happens when an output depends on a ratio, because dividing by a small number magnifies any change in it. Check the units first, then check whether the value you entered is in the range the relationship was designed for.
Do I have to fill in every field?
Only the fields a particular result depends on. If you leave one blank, the results that need it simply show a note instead of a number, and everything else still works.