Simple Interest Calculator
Quickly calculate non-compounding interest on personal loans, informal lending, or short-term investments.
Investment Details
Results
Principal
₹10,000
Total Interest
₹0
Total Amount
₹0
Every formula on this page is built to standard Indian banking and regulatory conventions (RBI guidelines, IBA formulas, current FY tax rules) and independently verified with worked numeric examples before publishing.
What is this Calculator?
A Simple Interest Calculator is the most basic financial tool for computing interest. Unlike compound interest, where you also earn interest on previously accumulated interest, simple interest is calculated strictly on the original principal amount, regardless of how much time passes.
How it Works
The formula is straightforward:
SI = (P × R × T) / 100
Where P is the Principal, R is the annual rate of interest (as a percentage), and T is the time period in years. The interest earned or charged is identical every year — it never grows on top of itself the way compound interest does.
Example Calculation
If you lend a friend or family member ₹1,00,000 at a simple interest rate of 8% for 5 years, the interest for each year is a flat ₹8,000. Over 5 years, the total interest is ₹40,000, making the final repayment amount ₹1,40,000.
Benefits of Using This Tool
- Informal or Family Loans: Ideal for calculating fair interest on loans between family members or friends, where a simple, transparent, non-compounding calculation is easier for both sides to verify.
- Easy to Understand: A linear, fully predictable calculation without exponential math — useful for quick mental-math-level estimates.
- Short-Term Instruments: Some short-term deposits and instruments in India are quoted using simple interest, making this useful for comparing against compounding alternatives.
Frequently Asked Questions (FAQs)
Do Indian banks use simple interest for loans?
Rarely, for standard loans. Almost all home loans, personal loans, car loans, and credit cards in India use compound interest on a reducing (amortizing) balance. Simple interest is more commonly seen in informal lending, some short-term instruments, and specific penalty interest calculations.
Is simple interest better for a lender or a borrower?
For a lender, compound interest earns more over time since interest builds on interest. For a borrower, simple interest is cheaper for the same nominal rate and time period, since you're never charged interest on interest already accrued.
How is simple interest different for a savings deposit vs a loan?
The math is identical either way — the formula doesn't distinguish between lending and depositing. What differs is who benefits: as a depositor, higher total interest works in your favor; as a borrower, lower total interest (via simple interest, when available) works in your favor.
Can I use this calculator to figure out my total repayment for an informal loan?
Yes. Enter the amount you're lending or borrowing, the agreed annual interest rate, and the number of years, and the calculator will show you both the total interest and the final repayment amount (principal + interest).
Sources & References
- Investopedia - Financial Calculation Standards
- Consumer Financial Protection Bureau (CFPB) Guidelines