Simple Interest Calculator
Calculate simple interest using the formula P x R x T / 100 on your investments and loans. View total interest, amount, and yearly breakdown with growth charts.
About This Calculator
This Simple Interest Calculator helps you quickly compute the interest earned or payable on any principal amount over a specified time period. It is ideal for savers evaluating fixed deposit returns, borrowers calculating loan costs, students learning financial mathematics, and anyone planning short-term investments. Simple interest is widely used across India, the US, and the UK for short-term loans, certain bonds, trade credit, and education loans.
Simple interest is calculated using the formula: SI = (P x R x T) / 100, where P is the principal amount, R is the annual interest rate (in percent), and T is the time period in years. The total amount at maturity is P + SI. Unlike compound interest, simple interest is calculated only on the original principal and does not earn interest on previously accumulated interest. This makes it predictable and easy to understand.
How to Use:
- Enter your principal amount -- the initial sum you invest or borrow
- Enter the annual interest rate (e.g., 8 for 8% per annum)
- Enter the time period in years -- can be fractional (e.g., 2.5 for two and a half years)
- Click Calculate to view total amount, interest earned, and yearly growth chart
- Share your calculation via the share button -- the URL encodes all inputs for easy sharing
Regional Notes:
India: Simple interest applies to certain bank FDs (though most now compound quarterly), education loans from public sector banks, post-office time deposits, and many government small savings schemes. Typical FD rates range from 5% to 8% for 1-5 year tenures.
US: Simple interest is used for some auto loans, personal loans, and short-term business loans. Many online savings accounts and CDs use compound interest instead. Typical simple interest loan rates range from 4% to 12% depending on creditworthiness.
UK: Simple interest applies to certain premium bonds, some mortgage products (interest-only), and student loans. The Bank of England base rate influences lending rates, with personal loan rates typically between 3% and 10%.
Frequently Asked Questions
What is simple interest and how is it calculated?
Simple interest is calculated only on the principal amount, not on accumulated interest. Formula: SI = (P x R x T) / 100, where P is principal, R is annual rate, and T is time in years. For example, ₹10,000 at 10% for 3 years: (10,000 x 10 x 3) / 100 = ₹3,000 interest. Total amount = ₹13,000.
What is the difference between simple and compound interest?
Simple interest is calculated only on principal, while compound interest includes interest on interest. ₹10,000 at 10% for 10 years: Simple interest = ₹20,000 total (₹10,000 interest), Compound interest = ₹25,937 total (₹15,937 interest). Compound interest yields significantly more over long periods.
When is simple interest used?
Simple interest is used for: Short-term loans (personal loans, car loans), Some fixed deposits (though most use compound), Educational loans, Government schemes with simple interest, Trade credit arrangements, Certain types of bonds. Most long-term investments use compound interest.
How to calculate simple interest on a loan?
For loans, simple interest = (Principal x Rate x Time) / 100. For a ₹5 lakh loan at 12% for 3 years: (5,00,000 x 12 x 3) / 100 = ₹1,80,000 interest. Total repayment = ₹6,80,000. Monthly EMI would be approximately ₹18,889 (total amount / 36 months).
What is the simple interest on ₹1 lakh for 5 years at 8%?
Simple interest = (1,00,000 x 8 x 5) / 100 = ₹40,000. Total amount = ₹1,40,000. This is linear growth - same interest each year (₹8,000 annually). With compound interest at same rate, the amount would be higher due to interest on interest.
Is simple interest better than compound interest?
For borrowers, simple interest is better as you pay less total interest. For investors, compound interest is better as you earn more. Simple interest is predictable and easier to calculate but yields lower returns over time. Compound interest accelerates wealth building significantly.
How does time period affect simple interest?
Simple interest grows linearly with time. ₹10,000 at 10%: 1 year = ₹1,000 interest, 5 years = ₹5,000 interest, 10 years = ₹10,000 interest. The interest amount is directly proportional to time - double the time, double the interest. Unlike compound interest, there's no acceleration.
What investments use simple interest?
Investments typically using simple interest: Some government small savings schemes, Certain types of bonds, Trade credit arrangements, Short-term fixed deposits (some banks), Educational loans (student loans). Most long-term investments like PPF, EPF, mutual funds use compound interest.
How to convert simple interest to compound interest?
You can't convert - they're different calculation methods. However, you can compare both for the same principal, rate, and time to see the difference. Use our compound interest calculator alongside simple interest to compare outcomes and understand the power of compounding.
What is the formula for total amount in simple interest?
Total Amount = Principal + Simple Interest. Simple Interest = (P x R x T) / 100. So, Total Amount = P + (P x R x T) / 100. For example, ₹10,000 at 10% for 3 years: Amount = 10,000 + (10,000 x 10 x 3) / 100 = 10,000 + 3,000 = ₹13,000.