Simple Interest Calculator
Calculate simple interest on your loans and investments with our free online Simple Interest Calculator. Get instant results for principal amount, interest rate, and time period. Perfect for understanding basic interest calculations on personal loans, education loans, and short-term deposits in India.
Calculate Simple Interest
Simple Interest Results
How Simple Interest is Calculated
Simple Interest is the most basic method of calculating interest on a loan or investment. Unlike compound interest, simple interest is calculated only on the original principal amount—it does not earn "interest on interest."
Simple Interest Formula
SI = (P × R × T) / 100
- SI = Simple Interest
- P = Principal Amount (initial amount)
- R = Rate of Interest (% per annum)
- T = Time Period (in years)
Total Amount = P + SI
When is Simple Interest Used?
Simple interest is commonly used in the following scenarios in India:
- Short-term personal loans: Many informal lending arrangements use simple interest
- Education loans: Some education loan schemes calculate interest simply during the moratorium period
- Car loans: Some dealerships offer simple interest financing
- Flat-rate loans: Small finance companies often use simple/flat interest rates
- Government savings schemes: Certain postal and government schemes
Simple Interest vs Compound Interest
The key difference is that simple interest remains constant throughout the loan tenure, while compound interest grows over time as interest is added to the principal. For borrowers, simple interest often means lower total interest paid. For investors, compound interest yields higher returns over long periods.
Example Simple Interest Calculation
Let's calculate simple interest on a typical loan:
Given Values
- Principal (P): ₹1,00,000
- Interest Rate (R): 8% per annum
- Time Period (T): 5 years
Step-by-Step Calculation
-
Apply the Simple Interest formula:
SI = (P × R × T) / 100 -
Substitute the values:
SI = (1,00,000 × 8 × 5) / 100 -
Calculate:
SI = 40,00,000 / 100
SI = ₹40,000 -
Calculate Total Amount:
Total Amount = Principal + Simple Interest
Total Amount = 1,00,000 + 40,000
Total Amount = ₹1,40,000
Result
- Simple Interest: ₹40,000
- Total Amount: ₹1,40,000
Over 5 years at 8% simple interest, you pay ₹40,000 as interest on a ₹1 lakh loan.
Comparison with Compound Interest
If the same ₹1 lakh was invested at 8% compound interest (compounded annually) for 5 years:
- Compound Interest: ₹46,933
- Maturity Amount: ₹1,46,933
The compound interest is ₹6,933 more than simple interest due to the "interest on interest" effect.
Quick Answers
What is simple interest?
Simple interest is interest calculated only on the principal amount for the entire period. It does not add previously earned interest back to the principal.
What is the simple interest formula?
Simple Interest = Principal × Rate × Time ÷ 100 (with rate in % per annum and time in years). For months or days, time is expressed as a fraction of a year.
When is simple interest used?
Simple interest is commonly used for short-term loans, some fixed-income products, and FDs with tenor below 6 months in India.
Simple interest vs compound interest?
Simple interest is computed only on principal; compound interest is computed on principal plus accumulated interest, so compound grows faster over time.
How do I convert tenure to years for the formula?
For months: divide by 12. For days: divide by 365 (or 366 in a leap year). Example: 6 months = 6/12 = 0.5 years.
Frequently Asked Questions
What is Simple Interest?
Simple Interest (SI) is a method of calculating interest where interest is computed only on the original principal amount throughout the entire loan or investment period. Unlike compound interest, simple interest does not add earned interest back to the principal, making calculations straightforward and predictable.
What is the difference between Simple Interest and Compound Interest?
Simple Interest is calculated only on the principal amount, while Compound Interest is calculated on the principal plus any accumulated interest. Over time, compound interest grows faster because you earn "interest on interest." For a ₹1 lakh investment at 10% for 3 years: Simple Interest = ₹30,000, but Compound Interest (annual) = ₹33,100.
Which loans in India use Simple Interest?
In India, simple interest is commonly used in: flat-rate personal loans from small finance companies, some education loan moratorium periods, dealer-financed car loans, informal lending, and certain government schemes. Most bank loans (home loans, personal loans) use reducing balance method which is a form of compound interest.
Is Simple Interest better for borrowers or lenders?
Simple interest is generally better for borrowers because the total interest paid is lower compared to compound interest for the same rate and tenure. For lenders/investors, compound interest is more beneficial as it yields higher returns over time. However, simple interest rates are often quoted higher to compensate, so always compare the total amount payable.
How do I calculate Simple Interest for months or days?
To calculate simple interest for periods less than a year, convert the time to years: For months, divide by 12 (e.g., 6 months = 6/12 = 0.5 years). For days, divide by 365 (e.g., 90 days = 90/365 = 0.247 years). Then apply the formula: SI = (P × R × T) / 100 with T in years.