Simple Interest Calculator
Calculate simple interest on your principal amount. Find the total interest earned and maturity amount for fixed-rate investments and loans.
* All calculations are approximate.
How Simple Interest Works?
Calculate simple interest on your principal amount. Find the total interest earned and maturity amount for fixed-rate investments and loans.
Simple interest is calculated only on the original principal amount, not on accumulated interest.
The interest remains the same every year since it is always computed on the initial principal.
Unlike compound interest, simple interest grows linearly — doubling the time doubles the interest.
Simple interest is commonly used in short-term FDs, Treasury Bills, and flat-rate loan calculations in India.
Formula Used
SI = P × R × T / 100
Where P = Principal amount, R = Annual interest rate (%), T = Time period in years
Important — Read Before You Decide
- Simple interest is calculated only on the original principal, unlike compound interest which includes accumulated interest
- Government of India Treasury Bills (T-Bills) and short-term FDs typically use simple interest calculations
- RBI Savings Bonds and certain post office schemes like the Kisan Vikas Patra historically used simple interest for specific tenures
- For the same rate and period, simple interest always yields less than compound interest — the gap widens with longer durations
- Flat-rate personal loans and car loans in India often advertise simple interest, but the effective rate is nearly double due to reducing balance
- Simple interest is commonly used in intra-day and short-term margin trading calculations by Indian brokers
- Section 80TTA of the Income Tax Act allows a deduction of up to ₹10,000 on interest from savings accounts (simple interest basis)
- Understanding simple vs compound interest is essential before comparing FD rates across banks in India
What Happens If You Ignore These?
- Choosing a simple interest product over a compound interest one for long-term goals leads to significantly lower returns
- Misunderstanding flat-rate loan interest as true interest rate results in paying more than expected
- Ignoring the interest calculation method when comparing two investment options can lead to poor financial decisions
- Not reinvesting simple interest proceeds means missing out on the benefits of compounding
Smart Tips
- Use simple interest calculations for short-term loans and deposits where the difference from compound interest is minimal
- When comparing loan offers, always ask whether the quoted rate is flat (simple) or reducing balance — a 10% flat rate is roughly equivalent to an 18-19% reducing rate
- For long-term wealth building, prefer compound interest instruments like PPF, mutual funds, and recurring deposits over simple interest products
- Use the formula P x R x T / 100 for quick mental estimates — e.g., ₹1,00,000 at 7% for 5 years = ₹35,000 interest
- Park emergency funds in savings accounts or liquid funds where simple interest applies, and invest long-term savings where compounding works in your favour
Frequently Asked Questions
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