Simple Interest Calculator

Our free Simple Interest Calculator helps you quickly compute the interest earned or paid on a principal amount over a given time period at a fixed annual rate. Just enter the principal, annual rate, and time — and get your result instantly.

What is Simple Interest?

Simple interest is a quick method to calculate the interest charge on a loan or the return on an investment. Unlike compound interest, it is calculated only on the original principal and does not include interest on previously earned interest.

Simple Interest Formula

The formula for simple interest is:

I = P × R × N / 100

• I = Interest Amount
• P = Principal Amount (original loan or investment)
• R = Annual Interest Rate (%)
• N = Time Period (years or months)

Example

If you invest $10,000 at an annual rate of 8% for 3 years:
I = 10,000 × 8 × 3 / 100 = $2,400

Frequently Asked Questions

Is simple interest better than compound interest?

For borrowers, simple interest is better as you pay less. For investors, compound interest is better as you earn more over time.

Can I use this calculator for monthly rates?

Yes. Enter the monthly rate in the Rate field and the number of months in the Time field.

Is this calculator free?

Yes, this simple interest calculator is completely free to use with no sign-up required.