Simple Interest Calculator
Enter principal, rate and time — get the interest instantly.
Interest Details
Simple Interest
The simple interest formula
Simple Interest = P × R × T, where P is the principal, R the annual rate, and T the time in years. Interest is always calculated on the original principal — unlike compound interest, it never earns interest on interest.
Simple Interest FAQ
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Simple Interest Calculator — clear, predictable interest
Simple interest is calculated only on the original principal, making it easy to predict and understand. It's used for short-term loans, savings bonds and many bank products. This calculator instantly computes interest and maturity for years, months or days.
Simple vs compound interest
Simple interest = P × R × T, where P is the principal, R the annual rate and T the time in years.
$1,00,000 at 8% simple for 5 years earns $40,000, maturing at $1,40,000.
Compound interest at the same rate and term earns $46,933 — the difference grows with time, which is why long-term investments prefer compounding.
Where simple interest is used
Short-term personal loans and payday advances.
Some government savings schemes and discount instruments (T-bills).
Bonds that pay a fixed coupon without reinvestment.
How to use this calculator
- Enter the principal amount.
- Input the annual interest rate (%).
- Choose the time period and unit (years, months or days).
- Read the simple interest and total maturity instantly.
Pro tips
- Convert months to years (÷12) and days to years (÷365) for precision.
- For any goal beyond 2–3 years, compound-interest products deliver meaningfully more.
- Check whether your loan uses simple or compound interest — it changes the total cost.