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Interest Calculator

Calculate simple interest on any loan or investment. Enter principal, rate, and time to see total interest earned or owed and the final amount.

Part of our Finance Calculators collection.

Interest Calculator

Free online calculator

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Results update automatically as you type

How to Use This Calculator

  1. 1

    Enter the principal (starting amount).

  2. 2

    Enter the annual interest rate.

  3. 3

    Enter the time period in years.

  4. 4

    See total interest and final amount.

Simple Interest Formula

Simple Interest = Principal × Rate × Time
I = P × r × t

Where r is the decimal rate (6% = 0.06) and t is in years.

Final Amount = Principal + Interest

Example Calculation

Example: $5,000 at 6% for 3 years

Inputs

principal: 5000rate: 6years: 3

Result

$900 interest | $5,900 total

I = $5,000 × 0.06 × 3 = $900. Total = $5,900.

Frequently Asked Questions

What is the difference between simple and compound interest?
Simple interest is calculated only on the original principal. Compound interest is calculated on principal plus accumulated interest. Over time, compound interest grows significantly faster.

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