Simple Interest Calculator

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About this calculator

This is an online simple interest calculator. This calculator not only gives you the answer but also the sample solution to find the answer.

This calculator uses the following simple interest formula, I:

simple interest formula


  • P is the principal
  • r is the interest rate (per year or per annum)
  • t is the loan duration/period in years.

Using this Calculator

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How to use this calculator

  1. Choose whether you want to calculate simple interest (I), principal (P), interest rate (r) or duration/period (t).
  2. Fill in the blue boxes with the required numbers.
  3. Click on the 'Calculate' button to calculate.

The sample answer and solution will be shown below the calculator.

I want to calculate

Interest (I)


Principal (P)


Interest Rate (r)


Duration (t)


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Sample Solution & Answer

The following are the sample solution and answer for your reference.

Ways to Use

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Using this calculator

You can use this calculator in many ways. Here are some ideas:

  1. Use it to check your homework answers.
  2. Use the sample solution as a guide to help you to solve questions that you are not sure about.