What is Simple Interest?
Simple interest is calculated only on the original principal — it does not include previously accumulated interest. The formula is SI = (P × R × T) / 100, where P is the principal, R is the annual interest rate, and T is the time in years. The total amount at the end of the period is P + SI.
Simple interest is commonly used in short-term loans, vehicle loans, and some bank deposits. It is straightforward to calculate and predictable, making it easy to plan repayments. However, for long-term investments, compound interest generally yields significantly higher returns because interest is reinvested each period.
When comparing loan products, always check whether the interest is simple or compound — the difference can be substantial over multi-year tenures, particularly at higher rates.
Frequently Asked Questions
What is the simple interest formula?
Simple Interest = (Principal × Rate × Time) / 100, where Rate is the annual interest rate in percentage and Time is in years. The total amount at the end is Principal + Simple Interest.
When is simple interest used?
Simple interest is commonly used for short-term personal loans, vehicle loans, and some government-backed schemes. It is also used when calculating interest for part of a year, such as on treasury bills or commercial paper.
Is simple interest better or worse than compound interest for borrowers?
Simple interest is always better for borrowers because you only pay interest on the original principal, not on accumulated interest. For the same principal, rate, and tenure, the total interest paid under simple interest is always lower than under compound interest.
How does simple interest differ from flat-rate interest on loans?
A flat-rate loan charges interest on the full original principal for the entire tenure, even as you repay it. This is equivalent to simple interest on the original amount. In contrast, reducing-balance EMI loans (like most home and car loans) charge interest only on the outstanding principal, which reduces each month.
Related Calculators
This calculator is for educational and illustrative purposes only. Actual loan or deposit terms may differ based on the financial institution and product agreement.