Simple Interest Calculator Calculators
Interest calculated on the original amount only — no compounding.
Simple Interest Calculator is a free online tool that interest calculated on the original amount only — no compounding. It runs entirely in your web browser using plain JavaScript, so files are processed on your own device and never uploaded to a server. There is no sign-up, no file size limit imposed by the site, no watermark and no paid tier.
- Price
- Free — no account, no quota, no watermark
- Category
- Calculators
- Where it runs
- In your browser, on your device
- Files uploaded
- None
- Technology
- plain JavaScript
- Settings
- 4
- Works offline
- Yes, after the first visit
About Simple Interest Calculator
Simple interest is charged only on the original principal, never on accumulated interest — P × r × t. It is rarer than compound interest in practice, showing up mainly in short-term loans, some bonds and certain legal and tax calculations where compounding is explicitly excluded.
How to use it
- Enter principal, annual rate and time (years).
- Adjust the remaining 1 setting if the defaults do not fit your case.
The 4 settings
| Setting | What it does | Default |
|---|---|---|
| Principal | A numeric value. | 10000 |
| Annual rate | A numeric value. | 5% |
| Time (years) | A numeric value. | 3 |
| Currency | Choose from 7: USD $, GBP £, EUR €, INR ₹, AUD A$, CAD C$…. | USD $ |
Under the hood
| Runs on | plain JavaScript — runs the whole thing |
| Controls | Principal, Annual rate, Time (years), Currency |
Questions
When would I actually meet simple interest?
Statutory interest on late commercial payments, some car finance and payday products, and Treasury bill style instruments. Most savings and mortgages compound, which grows considerably faster over long periods.
What does the currency option change?
It offers 7 choices — USD $, GBP £, EUR € and INR ₹ and more. The default is USD $, which suits most cases; change it when your input or your destination calls for something specific.
Is the arithmetic exact?
It uses double-precision floating point — about 15 significant figures, far more than the inputs justify. Displayed rounding is cosmetic; the underlying numbers are not rounded between steps, so chained results do not drift.