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Finance & business

Simple interest calculator

Calculate non-compounded interest from principal, annual rate and duration.

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  • Works offline
Interest—
Final amount—
Interest per year—

Interest = principal × rate × duration

Why use this tool?

Simple interest is calculated only on the original principal, so previously earned interest does not itself earn interest.

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Smart processing

Calculate and compare financial scenarios with clear indicators and explicit formulas.

Supported formats

Amounts, rates, terms and financial assumptions depending on the calculator.

Save time

Get a clean, ready-to-use result in seconds without installing software or configuring a complex workflow.

Fonctionnement

How does this tool work?

The calculator multiplies the original principal by the annual rate expressed as a decimal and then by the duration in years. That amount is the total interest for the period and is added to the principal to produce the final balance. Unlike compound interest, the calculation base never grows over time, so the increase is linear and the result remains straightforward to verify by hand.

Use cases

Short-term loan

Estimate financing cost when interest continues to be calculated only from the original borrowed amount.

Simple-interest investment

Project an investment where earned interest is paid out instead of being reinvested.

Learning and verification

Check a finance exercise with a transparent formula that can easily be reproduced manually.

Guide

How to use this tool

  1. 1

    Enter the principal

    Provide the starting amount on which interest will be calculated.

  2. 2

    Add the annual rate

    Enter the yearly percentage applied to the original principal throughout the period.

  3. 3

    Set the duration

    Enter the number of years to calculate accumulated interest and the final amount.

Tips and best practices

  • Make sure the entered rate is annual.
  • Use a decimal duration when the period is not a whole number of years.
  • Use the compound-interest calculator when interest is reinvested.

Frequently asked questions

How is it different from compound interest?

Compound interest is periodically added to the balance and then earns additional interest. Simple interest always uses only the original principal as its calculation base.

Can duration be decimal?

Yes. A duration such as 1.5 years is valid and is useful for representing partial years when the entered rate is annual.

Is the rate annual?

Yes. The tool treats the entered percentage as an annual rate, so monthly or quarterly rates should be converted before use.

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