Simple Interest Calculator
Work out simple interest and the total amount from a principal, rate and time in years or months.
About this calculator
Simple interest is interest charged only on the original principal, never on interest already earned. This free calculator instantly shows the interest and the total amount payable or receivable for any principal, rate and time period.
The formula
Simple Interest = P × R × T ÷ 100 — where P is the principal, R the annual rate in percent and T the time in years. The final amount is P + interest.
Worked example
A principal of ₹1,00,000 at 8% for 5 years earns ₹1,00,000 × 8 × 5 ÷ 100 = ₹40,000 in interest, for a total of ₹1,40,000.
For savings that compound, use the compound interest calculator instead, or the FD calculator for bank deposits.
Why use this simple interest calculator
The clean P·R·T formula
Simple interest is charged only on the principal, never on accumulated interest — the tool gives the exact figure without compounding creeping in.
Interest and total in one view
See both the interest alone and the total amount repayable, so you know the full cost or return at a glance.
Any period
Works for days, months or years, which suits short informal loans and quick estimates.
Common use cases
- Work out interest on a personal or family loan
- Check the interest on a short-term deposit quoted at simple rate
- Compare a simple-interest quote against a compounding one
- Teach or check the basic interest formula
Frequently asked questions
Simple interest = (P × R × T) ÷ 100, where P is the principal, R is the annual interest rate in percent, and T is the time in years. The total amount is principal plus interest.
Simple interest is calculated only on the original principal, so it stays the same each year. Compound interest is calculated on the principal plus accumulated interest, so it grows faster over time.
Yes. Switch the time unit to months and the calculator converts it to years automatically before applying the formula.
It is common for short-term loans, car loans, some fixed deposits and informal lending where interest does not compound.
No. The calculation runs entirely in your browser and nothing is uploaded or stored.
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