Simple Interest Calculator
Interest on the original amount only, with the compound figure beside it.
Everything runs inside your browser. Your files never leave your device.
Result
Ask about Simple Interest Calculator
Questions about what this tool does, which option to pick, or what it can and cannot handle.
The question you type here is sent to an AI provider to be answered — your files and whatever you put in the tool above are not, and the assistant cannot see them. Answers are generated and can be wrong. The tool itself is not guessing: it runs deterministic code on your device.
About the Simple Interest Calculator
Simple interest is charged on the original amount and nothing else. Borrow a lakh at eight per cent for five years and the interest is forty thousand — eight thousand a year, five times, with no interaction between the years.
Its usefulness today is mostly as a comparison. Almost nothing in modern finance actually works this way: bank deposits compound, loans reduce, and the few products that quote a flat figure are quoting it precisely because the number looks smaller than the equivalent compound one. So this tool prints both, and the difference between them is the point of the page.
Over short periods the two barely diverge. At eight per cent for one year they are identical, and at two years the gap is under a thousand rupees on a lakh. Push the term to fifteen years and the compound figure is roughly double the simple one. The divergence is a function of time far more than of rate, which is why a flat quote on a long loan is so much more misleading than the same quote on a short one.
Where you will genuinely meet simple interest is in loans between individuals, some short-term business advances, certain deposit schemes that pay interest out rather than reinvesting it, and the interest component of a few tax provisions. In each of those cases the number here is the whole answer rather than a comparison.
If you are looking at a lender quoting a flat rate on an instalment loan, the tool you actually want is the flat versus reducing comparison, which converts the quote into the rate you are really paying.
How to use it
- 1Enter the principal, the rate and the number of years.
- 2Read the interest and the total repayable.
- 3Look at the compound figure printed underneath and note the gap.
- 4Stretch the term and watch the gap widen — that widening is the whole argument for compounding.
Questions
- When would I actually use simple interest?
- Loans between individuals, short business advances, deposit schemes that pay interest out rather than reinvesting it, and certain statutory interest calculations. Outside those, compounding is the norm.
- Why show the compound figure as well?
- Because the comparison is the useful part. A rate quoted on a simple basis and the same rate quoted on a compound basis are not the same offer, and on a long term they are not even close.
- Is a flat loan rate the same as simple interest?
- The interest is calculated the same way, on the full original amount for the full term. But because you repay the loan in instalments, you are paying that interest on money you no longer have, which makes the effective cost far higher than the quote. The flat versus reducing tool works out by how much.
- Does the gap depend more on the rate or the term?
- The term, decisively. Doubling the rate widens the gap; doubling the years widens it far more, because compounding feeds on itself and simple interest never does.