Free Simple Interest Calculator Online
Calculate simple interest and total payable amount from principal, annual rate and time period. Fast, free and 100% private.
About the Simple Interest Calculator
Simple interest is the most straightforward method of calculating interest on a loan or investment. It is computed solely on the original principal amount — interest does not accumulate on previously earned interest.
The formula is: SI = (P × R × T) / 100, where P is the principal, R is the annual interest rate in percent, and T is the time period in years. The total amount payable or receivable is P + SI.
Simple interest is commonly used in short-term personal loans, savings accounts, fixed deposits with periodic payouts, and government savings schemes such as NSC and PPF (for basic illustrations). When comparing loan products, understanding simple vs compound interest helps you make better financial decisions.
How to Use the Simple Interest Calculator
Enter Principal Amount
Enter the initial loan or deposit amount in rupees.
Enter Interest Rate
Enter the annual interest rate (%) as stated in your loan or savings agreement.
Enter Time Period
Enter the duration in years or months. The calculator automatically converts months to years.
Click Calculate
Instantly see the simple interest earned and the total amount payable, along with the formula used.
Frequently Asked Questions
The formula is SI = (P × R × T) / 100, where P is the principal amount, R is the annual interest rate as a percentage, and T is the time period in years. The total amount is A = P + SI.
Simple interest is calculated only on the original principal, so the interest amount stays the same each period. Compound interest is calculated on the principal plus all accumulated interest, causing the interest to grow over time. For the same principal, rate and time, compound interest always results in a higher final amount than simple interest.
Yes, this simple interest calculator is completely free to use with no registration or sign-up required. It runs entirely in your browser, so no data is ever sent to any server.
Yes. Your principal, rate, time and time unit are saved to your browser's localStorage and automatically restored the next time you open the page. Nothing is stored on any server — all data stays local to your device.