Simple interest calculator
Calculate interest from principal, rate and time.
Simple interest calculator
Your result appears here
Adjust the values to see your result automatically.
How to use Simple interest calculator
The Simple interest calculator takes a principal, an annual percentage rate and a time in years and returns the interest and the ending balance. It applies interest = principal × rate / 100 × years and adds it to the principal, with no compounding. Partial years work as decimals, so six months is entered as 0.5.
- Adjust the values; an initial result is calculated from the defaults.
- Change the basic settings or open Advanced mode to fine-tune the result.
- Review and copy or download your result. Pause Live results to run manually. Sources or individual settings above 20,000 characters require an explicit run.
What this tool supports
Calculate interest from principal, rate and time.
- Principal
- Range: 0 to no maximum
- Annual rate (%)
- Range: 0 to no maximum
- Years
- Range: 0 to no maximum
Limits and processing
Use finite numbers, valid dates and the ranges shown by each control. Invalid values produce an error without a downloadable result.
Frequently asked questions
What is the simple interest formula?
Interest equals principal × annual rate / 100 × years, and the ending balance is principal plus that interest. For 10,000 at 5% for 3 years, interest is 1,500 and the ending balance is 11,500. The result also shows the formula with your values.
How do I calculate simple interest for months instead of years?
Convert months to a fraction of a year and enter that in the Years field. Six months is 0.5 years and 18 months is 1.5 years. The rate is always treated as a yearly percentage.
What is the difference between simple and compound interest?
Simple interest is charged only on the original principal, so it grows by the same amount every year. Compound interest also earns interest on previously added interest. This calculator does not compound, so use a compound interest calculator for that case.
Where is my input processed?
This operation processes its source in your browser. Copy and download are explicit actions; source input is not saved in an account or history.
What are the input limits?
Use finite numbers, valid dates and the ranges shown by each control. Invalid values produce an error without a downloadable result.