PopularHot
EMI Calculator
Use EMI Calculator to plan with confidence — instant, transparent calculations.
CalculatorOpen Tool
Simple Interest Calculator
Work out flat simple interest — charged only on the principal, with no interest on interest. ₹, live in your browser.
Loading Simple Interest Calculator…
Your browser is preparing the tool. It runs 100% locally.
Quick Answer
Enter a principal, an annual rate and a number of years, and it returns the simple interest and the total amount using SI = P × R × T ÷ 100. Simple interest is flat — charged only on the original principal, never on accrued interest — so ₹1,00,000 at 8% for 5 years earns exactly ₹40,000, and the total is ₹1,40,000. It runs live in your browser.
What the Simple Interest Calculator Does
Put in a principal, an annual rate and a number of years, and the tool shows the simple interest and the total you'd repay or receive. It recalculates instantly and works in rupees.
The defining feature is that it's linear: the interest is the same every year, because it's always a percentage of the original principal, not of a growing balance. That makes it easy to predict and, on a loan, cheaper than compound interest.
How It Works
It applies the simple interest formula SI = P × R × T ÷ 100, where P is the principal, R the annual rate as a percentage and T the time in years.
The total is just the principal plus that interest. Because nothing compounds, doubling the term doubles the interest — there's no acceleration over time.
Methodology
- Step 1. Take the principal P, the annual rate R (as a percentage), and the time T in years.
- Step 2. Compute SI = P × R × T ÷ 100.
- Step 3. Report the simple interest and the total amount, which is P + SI.
- Step 4. Recompute live whenever an input changes.
Simple interest
SI = P × R × T ÷ 100
Total = P + SI
(P = principal, R = annual rate %, T = years)Worked examples
₹1,00,000 at 8% for 5 years: 100000 × 8 × 5 ÷ 100 = ₹40,000 (total ₹1,40,000)Each year adds the same ₹8,000 — the 'flat' in flat interestBecause the interest is always on the original ₹1,00,000, the yearly amount never changes. Compound interest on the same figures would earn more, since it adds interest on the interest.
Assumptions
- Interest is charged on the original principal only — nothing compounds.
- A fixed annual rate for the whole term.
- No part-payments, fees or tax are applied.
- Time is in years; for months, enter a fraction (6 months = 0.5).
Technical Details
| Inputs | Principal, annual rate %, years |
|---|---|
| Outputs | Simple interest, total amount |
| Growth | Linear (flat) |
| Currency | Rupees (₹) |
| Formula | SI = P × R × T ÷ 100 |
| Where it runs | In your browser, live |
Standards & references
- SI = P × R × T ÷ 100 — the standard simple interest formula, giving interest only on the principal.
- Linear growth — equal interest each period, so the total rises in a straight line rather than a curve.
- Common use — many car, personal and student loans, and some bonds, charge simple interest — and it usually means less total interest than compounding.
Accuracy & Limitations
It's flat interest only. If your product compounds — most savings accounts and fixed deposits do — this understates the result; use the compound interest or FD calculator instead.
It assumes a constant rate and no part-payments; a loan you prepay accrues less than this shows.
Time is in years. For a period in months, enter the fraction — 9 months is 0.75.
The figure is gross, with no tax or fees taken out.
Real-World Use Cases
Simple-interest loans
Estimate interest on a car, personal or other flat-rate loan.
Quick flat sums
Get a fast, predictable interest figure for a short term.
Compare quotes
Set a flat-rate offer against a compounding one to see the gap.
Teach the basics
Show how flat interest differs from compounding.
When to use it — and when not to
Good for
- Flat-interest loans and quotes
- Quick, predictable interest sums
- Comparing against a compound figure
- Learning simple vs compound
Not the best choice for
- Accounts that compound (savings, FD)
- Recurring monthly investments
- After-tax figures
Money that compounds? Use the compound interest calculator. A bank fixed deposit? Use the FD calculator (quarterly compounding). Investing monthly? Use the SIP calculator.
Frequently Asked Questions
What is the simple interest formula?
SI = P × R × T ÷ 100, where P is the principal, R the annual rate as a percentage and T the time in years. The total amount is P + SI.
How is it different from compound interest?
Simple interest is charged only on the original principal, so it grows in a straight line. Compound interest is charged on the principal plus accrued interest, so it grows faster over time.
When is simple interest actually used?
On many car, personal and student loans, and on some bonds. For a borrower it's usually cheaper than compound interest over the same term.
What does ₹1,00,000 at 8% for 5 years earn?
Exactly ₹40,000 — that's 100000 × 8 × 5 ÷ 100. The total becomes ₹1,40,000, and each year contributes the same ₹8,000.
How do I enter a period in months?
As a fraction of a year. Six months is 0.5, nine months is 0.75, eighteen months is 1.5, and so on.
Does it compound?
No, and that's the point. The interest never earns interest, which is exactly what makes it simple rather than compound.
Is simple interest cheaper on a loan?
Over the same rate and term, yes — because there's no interest on interest, the total is lower than a compounding loan.
Is tax deducted?
No. The figure is gross, before any tax or fees.
Is the rate fixed?
Yes — it assumes one constant annual rate for the whole term.
What's the difference between interest and total?
The interest is what's added; the total is the principal plus that interest — what you'd repay on a loan or hold at the end of a deposit.
Why does my savings account earn more than this shows?
Because it compounds. Savings and fixed deposits add interest to the balance and then pay interest on it, which this flat calculation doesn't.
What currency does it use?
Rupees, but the formula is the same for any currency — only the units change.
References
Computes flat interest with SI = P × R × T ÷ 100 — charged only on the original principal, so it's linear and, unlike compound interest, never earns interest on interest.
Related Tools
PopularHot
BMI Calculator
BMI Calculator online: fast, accurate numbers for smarter decisions.
CalculatorOpen Tool
Popular
Loan Calculator
Loan Calculator with live results and the exact formula shown — free and accurate.
CalculatorOpen Tool
Popular
Percentage Calculator
Percentage Calculator online: fast, accurate numbers for smarter decisions.
CalculatorOpen Tool
Popular
Age Calculator
Use Age Calculator to plan with confidence — instant, transparent calculations.
CalculatorOpen Tool
Popular
Discount Calculator
Discount Calculator online: fast, accurate numbers for smarter decisions.
CalculatorOpen Tool
Ready to try the Simple Interest Calculator?
It is free, private and runs entirely in your browser — no sign-up, no uploads, no limits.