Calculate simple interest on principal amount
Simple interest is a straightforward method of calculating interest on a loan or investment. It is calculated solely on the original principal amount, meaning the interest amount remains constant for each period throughout the duration of the loan or investment.
The formula for simple interest is: SI = (P × R × T) / 100, where SI is the Simple Interest, P is the Principal amount, R is the annual interest rate (as a percentage), and T is the time period in years.
Simple interest is calculated only on the original principal amount. Compound interest is calculated on the principal plus any accumulated interest from previous periods. Over time, compound interest grows exponentially, while simple interest grows linearly.
Simple interest is commonly used in short-term personal loans, auto loans, Treasury bills (T-bills), commercial trade finance, and short-term certificates of deposit (CDs). It is also used during grace periods for certain student loans.
Convert the time period into years. For months, divide the number of months by 12 (e.g., 6 months = 0.5 years). For days, divide the number of days by 365 (e.g., 90 days = 90 / 365 ≈ 0.247 years) or by 360, depending on banking conventions.
Simple interest generally favors borrowers because it accumulates slower than compound interest, resulting in lower total interest payments over time. Lenders and investors usually prefer compound interest because it generates higher returns.
On a simple interest loan, interest is calculated daily based on the unpaid principal balance. If you make payments on time, the interest is paid off first, and the remaining amount reduces the principal. Paying early or paying extra reduces the principal faster, saving you money on interest.
Simple interest is calculated on the remaining balance of the loan. Amortized interest is structured with equal monthly payments where the proportion going towards interest vs. principal changes over time (more interest is paid in the early stages of the loan).
Most standard savings accounts and high-yield savings accounts (HYSAs) in the US and India use compound interest (typically compounded daily and credited monthly) rather than simple interest. However, some short-term promotions may offer simple interest terms.
In both the US and India, simple interest earned on investments is taxable. In the US, it is taxed as ordinary income and reported on Form 1099-INT. In India, it is classified under 'Income from Other Sources', with TDS (Tax Deducted at Source) deducted if annual interest exceeds specified limits.
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