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Simple Interest — Free Online Tool
Simple interest is interest calculated only on the original principal, never on interest that has already been earned. That makes it the easiest way to work out the cost of a short personal loan, the return on a basic deposit or the answer to a school maths question. This calculator takes the principal amount, the annual rate of interest and the time in years, then returns the interest earned and the total amount payable using the formula SI = P × R × T ÷ 100. A principal of ₹10,000 at 5% for two years, for instance, earns ₹1,000 in interest for a total of ₹11,000. Simple interest is common in informal lending between friends and family, some vehicle and consumer loans advertised with a flat rate, and many textbook problems for Class 7 to 10 and competitive exams. Keep in mind that most bank fixed deposits and savings products in India compound interest, and flat-rate loans have a higher effective cost than their headline number suggests, so compare the two methods before deciding. Use the Compound Interest calculator when interest is added back to the balance. The page runs in your browser with no sign-up.
Use our Simple Interest on AllConvertor — no registration, no download, works on iPhone, Android, Windows, and Mac. All processing runs in your browser when possible for maximum privacy and speed.
How to use Simple Interest
- Enter the principal amount.
- Type the annual interest rate in percent.
- Enter the time period in years, using decimals for months.
- Read the interest earned and the total amount below.
Key benefits
- ✓ 100% free — no paywall or trial limits
- ✓ No account or email required
- ✓ Mobile-friendly responsive design
- ✓ Instant results in your browser
- ✓ Secure — data stays on your device
- ✓ Trusted by thousands of users daily
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Frequently Asked Questions
What is the formula for simple interest?
Simple interest equals Principal × Rate × Time ÷ 100, where the rate is the yearly percentage and time is in years. The total amount is principal plus interest.
How do I calculate simple interest for months?
Convert months to years by dividing by 12 before entering the time. Eight months is 8 ÷ 12 = 0.6667 years.
What is the difference between simple and compound interest?
Simple interest is earned only on the original principal, while compound interest is earned on the principal plus previously accumulated interest, so it grows faster over longer periods.
Do Indian banks use simple interest?
Most fixed deposits and recurring deposits compound interest quarterly, and home loans use a reducing balance. Simple interest is used in some informal loans, flat-rate loans and many exam problems.
Can I find the rate or time instead of the interest?
Rearrange the formula: Rate = SI × 100 ÷ (P × T) and Time = SI × 100 ÷ (P × R). This calculator is built for finding the interest and total amount from the three known values.