Simple Interest Calculator
Calculate simple interest and the total amount on any principal, rate and time.
- Principal
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- Total amount
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What is simple interest?
Simple interest is interest charged only on the original principal, never on the interest already earned. It is used for many short-term loans, fixed deposits quoted on a simple basis, and everyday calculations where the interest does not compound. Because it ignores compounding, it is the easiest interest to work out.
The simple interest formula
Interest = P × R × T ÷ 100, where P is the principal, R is the
annual rate of interest and T is the time in years. The total amount you get back is simply
P + interest. This calculator does both steps for you.
How to use the Simple Interest Calculator
- Enter the principal. Type the original amount you invest or borrow.
- Add the interest rate. Use the annual rate of interest as a percentage.
- Set the time period. Enter the duration in years — decimals like 1.5 are fine.
- Read the result. See the interest earned and the total maturity amount instantly.
Frequently asked questions
How is simple interest different from compound interest?
Simple interest is calculated only on the principal. Compound interest is calculated on the principal plus previously earned interest, so it grows faster over time.
Can I use months instead of years?
Enter the time in years. For 6 months use 0.5, for 18 months use 1.5, and so on.
Where is simple interest actually used?
It is common for short-term personal loans, some car loans, and certain fixed deposits or bonds that pay interest without reinvesting it.
Does this store my numbers?
No. The calculation runs entirely in your browser; nothing you enter is sent to or stored on a server.