Simple interest and maturity calculator
Calculate simple interest and maturity value, and compare it with the same principal compounding annually at the same rate.
Simple interest
₹37,500
Maturity value
₹1,37,500
Same rate, compounded yearly
₹1,43,563
How to use simple interest calculator
- 1Enter your numbers in the fields above. The result updates as you type — there is no calculate button to press and nothing is submitted anywhere.
- 2Check the assumptions shown under the result. A calculator is only as good as the rate, term and rounding it assumes, and those are stated rather than buried.
- 3Read the working, not just the headline figure. Where a calculation has components — interest, principal, tax, slab — they are shown separately so the answer can be checked by hand.
- 4Note the figure down before you close the tab: nothing is stored, so a result you forget to note is gone.
Why this tool, and why browser-side
Calculators are the tools people return to — a loan decision this month, a tax check at year end, a BMI reading at a clinic visit. Reaching for a page that uploads nothing and logs nothing makes the return visit a comfortable one.
Every calculation runs in your browser as you type. There is no request in flight, so there is no privacy-policy asterisk to read: the salary, the loan amount, the medical figures and the dates you enter are never transmitted.
Results are shown with the working rather than as a bare number. That matters when a loan officer, a school form or a tax portal wants the figure to be justifiable, and it matters more when the figure is one you are going to argue with.
The simple interest calculator on this page is deliberately narrow: it answers one question, states the assumptions beside the answer, and does not ask for an email or an account first. That is the whole design — a calculator you can open, use and close without leaving anything of yourself behind.
The numbers you type into a calculator are among the most sensitive figures in your life: income, loans, outstanding balances, medical measurements, in some cases a diagnosis. That is the strongest argument for a calculator that runs entirely in the tab. Close this page and the numbers are gone from memory, because there was nowhere else for them to go.
Money calculators are only as good as the assumptions behind them, which is why the assumptions are shown next to the answer rather than buried in a footnote. A compound interest projection assumes the rate holds for the entire term, and no rate in India is guaranteed like that — PPF is re-notified every quarter and deposit rates change with the policy cycle. Treat a projection as a planning scenario and check the current rate before you commit money to it.
Accepted inputs are PDF files up to 50 MB. SVG, HTML and other script-bearing formats are refused outright rather than sanitised, because a file that can execute code has no business being re-encoded — and an upload field that accepts one is a security hole rather than a feature. The tool works on one file at a time, which keeps the result unambiguous.
How it works under the hood
The arithmetic follows the published formulas rather than approximations: loan instalments use the standard reducing-balance annuity formula; recurring and fixed deposits compound at the frequency the instrument specifies; tax and slab figures are applied in the order the statute defines, including surcharge and cess where relevant; age is computed on the calendar by borrowing months the way an eligibility clause does, not by dividing total days. All of it is evaluated in your browser with double-precision floating point, and each result is rounded only for display, which is why the figure you see and the figure you recompute agree to the rupee. The calculation runs locally in your browser. The page or its code may still require a connection to load, and offline use is not guaranteed. Review the assumptions and independently verify important decisions.
Frequently asked questions
Why is the compound figure so much larger?
Simple interest never earns on its own interest, so the gap widens with term and rate. Over ten years at 7.5% on one lakh, compounding earns roughly 45,000 more than simple interest — and that gap is what a flat-rate loan quotation hides.
Are these results financial or medical advice?
No. They are arithmetic on the numbers you supply, with the assumptions stated. A projection is not a forecast, a tax figure follows rules recorded at a stated date, and BMI is a screening indicator rather than a diagnosis.
Do you store the numbers I type?
No. The calculation runs in the page with no request in flight, so there is nothing to store on our side. Refreshing the page clears everything — which is also why we cannot recover a calculation you forgot to note down.
How current are the rates and slabs?
Each rate or slab carries the date it was recorded and the source it came from. Tax and interest rates change, so the page tells you to verify against the official source before acting on a figure — that instruction is not legal boilerplate.
Why does the calculator show more than one number?
Because the single figure is rarely the useful one. A loan is not its EMI but its total interest; a tax regime comparison is not one regime's tax but the difference between two; a BMI is not the index but the index next to the waist measurement.
Can I use this on a phone?
Yes. The layout is responsive and the fields accept numeric keyboards, so entering figures on a phone is no more awkward than on a desktop. Nothing depends on a desktop-only feature.
Do I need to create an account?
No. There are no accounts, no cookies for the calculator, and no email required. The tool is a page of arithmetic, and it behaves like one.
Does it work offline?
Once the page has loaded, yes. The calculation is local JavaScript with no dependencies, so a dropped connection does not affect it.