Finatune
Back to all calculators

Simple Interest Calculator — Calculate Interest Quickly

Calculate simple interest on loans or savings using the formula I = P × r × t. Enter principal, rate, and time to see your total interest and final amount.

Quick Answer

To calculate simple interest, multiply the principal by the annual interest rate (as a decimal) by time in years: I = P × r × t. For example, $10,000 at 5% for 3 years gives $1,500 in interest and a total of $11,500. Enter your values above to get an instant result.

$
%
Years
Months
Interest Calculation
I = P × r × t
Principal Amount
$10,000
Annual Interest Rate5% per year
Time Period3 years (3 years)
Total Interest Earned
$1,500
Total Amount (Principal + Interest)$11,500

How to Use This Calculator

Enter the principal amount (initial money), the annual interest rate as a percentage, and the time period. Choose between years or months for the time unit. The calculator applies the simple interest formula I = P × r × t automatically. Results update instantly as you adjust any value. Use this simple interest calculator for loans, savings, or any interest calculation.

How Simple Interest Works

Simple interest is calculated using the formula I = P × r × t, where I is interest, P is principal, r is the annual interest rate (as a decimal), and t is time in years. Unlike compound interest, simple interest is calculated only on the original principal, not on accumulated interest. This makes it straightforward and predictable for short-term loans, bonds, and basic savings accounts. For example, $10,000 at 5% for 3 years earns $1,500 in interest, for a total of $11,500.

FAQ

Related Calculators

Related Guides & Tips

→ Simple vs. Compound Interest: What to Know→ Understanding Interest Rates on Loans→ How to Save Money Effectively

Also try our free Budget Planner template

Create and manage your monthly budget with the 50/30/20 rule. Track income, expenses, and savings in one place.

Download Budget Planner