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Simple Interest Calculator

Calculate simple interest (I = P × R × T) and the total amount, with time in years, months or days.

Enter values

Results update as you type.

Result

Interest

$1,800.00

Total amount
$11,800.00
Step-by-stepShow
  1. I = 10,000 × 6% × 3 yr = 1,800

About the Simple Interest Calculator

Calculate simple interest (I = P × R × T) and the total amount, with time in years, months or days.

Also known as: si calculator, simple interest formula, prt calculator, flat interest.

How to use this calculator

  1. Enter principal, annual interest rate, time, time unit.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Open “Step-by-step” to see how the answer was worked out.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

I = P × R × T / 100 · A = P + I

Worked example

Using the values pre-filled in the calculator above:

  • Principal = 10,000
  • Annual interest rate = 6 %
  • Time = 3
  • Time unit: Years

the calculator returns:

  • Interest: 1,800
  • Total amount: 11,800

Working

  1. I = 10,000 × 6% × 3 yr = 1,800

Frequently asked questions

What is the difference between simple and compound interest?

Simple interest is charged only on the original principal. Compound interest is also charged on interest already earned, so it grows faster over time.