Simple Interest Calculator
Calculate simple interest, total amount, and compare with compound interest for any loan or deposit.
Simple interest calculator applies the SI formula: P × R × T / 100. Enter the principal, annual interest rate, and time period in years. Get the interest earned, total amount payable, and a side-by-side comparison with compound interest at the same rate. Useful for short-term loans, personal finance comparisons, and exam problems. Free, no signup required.
Simple Interest
Interest earned
₹25,500
₹25,500
Total amount
₹1.25 L
₹1,25,500
Compound Interest (quarterly, for comparison)
CI earned
₹28,702
₹28,702
CI total amount
₹1.29 L
₹1,28,702
CI earns more by
₹3,202
Compounding quarterly vs SI at 8.5% for 3 yr
Frequently Asked Questions
- What is the simple interest formula?
- Simple Interest = Principal × Rate × Time / 100. For ₹50,000 at 8% per annum for 3 years, SI = 50,000 × 8 × 3 / 100 = ₹12,000. The total amount at maturity is Principal + SI = ₹62,000.
- How is simple interest different from compound interest?
- Simple interest is calculated on the original principal throughout the tenure. Compound interest is calculated on the growing balance, adding interest to principal each period. For ₹1 lakh at 10% over 5 years, SI gives ₹50,000 and CI (quarterly) gives around ₹63,862. The difference grows with longer tenures.
- Is simple interest used in bank loans in India?
- Most bank loans in India use reducing balance interest, not flat simple interest. Personal loan ads that show a flat rate of 14% p.a. are using simple interest on the original principal. The effective interest rate is nearly double. Banks must disclose the APR (Annual Percentage Rate) under RBI guidelines for fair comparison.
- How do I calculate simple interest per month?
- Divide the annual rate by 12 to get the monthly rate. For ₹10,000 at 12% per annum, monthly rate = 1%. Monthly SI = 10,000 × 1 / 100 = ₹100. Alternatively, enter time as a fraction in the calculator. Enter 0.5 for 6 months or 0.25 for 3 months.
- What is SI for ₹1 lakh at 7% for 2 years?
- SI = 1,00,000 × 7 × 2 / 100 = ₹14,000. Total amount = ₹1,14,000. Enter these values in the calculator to confirm and also see how compound interest compares at the same rate.
- What is the difference between flat rate and reducing balance interest?
- Flat rate (simple interest) charges interest on the full original principal for every month. Reducing balance charges interest only on the outstanding principal after each payment. A 12% flat rate loan costs around 21-22% effective annual interest. Reducing balance at 12% costs exactly 12% annually. All home loans and most personal loans use reducing balance.
What is Simple Interest Calculator?
Simple interest calculator applies the SI formula to find the interest earned on any principal over a fixed tenure. SI stands for Simple Interest. Banks, lenders, and investors use it as a baseline for understanding interest before factoring in compounding.
The tool also shows compound interest at the same rate for the same tenure. The comparison makes the effect of compounding concrete and numerical.
How does it work?
The formula is SI = P × R × T / 100. P is the principal, R is the annual interest rate as a percentage, and T is the time in years. Total amount = P + SI.
For ₹75,000 at 9% per annum over 4 years: SI = 75,000 × 9 × 4 / 100 = ₹27,000. Total amount = ₹1,02,000.
For the compound interest comparison, the tool uses quarterly compounding. The formula is A = P × (1 + R / (4 × 100))^(4 × T). Quarterly compounding is the most common frequency used by Indian banks for fixed deposits and savings accounts.
The difference between CI and SI grows with time and rate. Over 1 year at any rate, the difference is small. Over 10 years at 12%, CI adds thousands of rupees more than SI.
Simple Interest Calculator in India
Simple interest appears in specific financial products in India. Government bonds and some NSC (National Savings Certificates) under the post office scheme pay simple interest on the face value. Gold loans from NBFCs often advertise flat interest rates, which are effectively simple interest on the full loan amount.
Personal loan advertisements frequently quote flat interest rates. An 18% flat rate personal loan costs about 32-33% effective interest per year when calculated on the reducing balance. RBI guidelines require lenders to disclose the APR (Annual Percentage Rate), which accounts for the reducing balance effect. Always compare personal loans by APR, not the flat rate.
In competitive exams, SI questions are among the most common. UPSC, SSC, IBPS, and state PSC papers regularly test the SI formula. Students use the formula to find any of the four variables given the other three. Rearranged forms: P = SI × 100 / (R × T). R = SI × 100 / (P × T). T = SI × 100 / (P × R).
Tips to get the best results
- For time periods under a year, enter the fraction directly. Six months is 0.5 years. Three months is 0.25 years. The formula handles fractional years correctly.
- For monthly interest calculations, set the rate to the annual rate and time to 1/12 (or 0.0833). The result is the monthly interest on the principal.
- Compare SI and CI results carefully. For tenures above 3 years, the CI total amount is noticeably higher. Longer tenure amplifies the advantage of compounding.
- When evaluating gold loans or personal loans that quote flat rates, use this calculator. Compute SI at the flat rate, then compare the total payout to an EMI-based loan at a lower stated rate.
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