Simple interest calculator
Calculate simple interest, final amount, rate or time, with the I = P × r × t formula explained.
How to useI = P × r × t
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Simple interest calculator: what it is for
The calculator solves any simple interest problem: find the interest and final amount, or find the principal, rate or time from the other values. Rate and time can be in days, months or years.
The formula used appears below the result.
How to use
- Choose what you want to find.
- Fill in the other values.
- See the result and the formula.
When to use it
- Financial math exercises.
- Calculating late fees and interest.
- Simple personal loans.
Frequently asked questions
What's the difference between simple and compound interest?
With simple interest, interest is charged only on the initial amount. With compound interest, it's also charged on accumulated interest (interest on interest), so it grows faster.
Where is simple interest used?
In late fees on bills, some personal loans between people and financial math exercises.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 tools are free and run right in your browser.