Simple Interest Calculator
Calculate interest using the formula SI = P × R × T / 100
Results
Adjust the inputs and click Calculate.
Frequently Asked Questions
Total Amount (A) = P + SI
Where P = Principal, R = Annual interest rate (%), T = Time (years).
For months: T = months / 12. For days: T = days / 365.
P = (SI × 100) / (R × T)
R = (SI × 100) / (P × T)
T = (SI × 100) / (P × R)
Enter any three known values in this calculator and adjust until you match your target interest amount.
About This Simple Interest Calculator
This free simple interest calculator lets you instantly compute the interest earned or owed on any principal amount. Enter the principal, annual interest rate, and time period (in years, months, or days) to get the total interest, final amount, and a period-by-period breakdown table.
Simple interest is the most straightforward form of interest calculation. It is widely used in short-term loans, car financing, government bonds, and informal lending. Because interest does not compound, the total interest grows linearly — making it easy to plan and predict repayments.
When to use this calculator
- Calculating interest on a short-term personal loan
- Estimating returns on treasury bills or CDs
- Comparing simple vs compound interest for the same rate
- Computing daily or monthly interest for any amount
Standards & References
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