Simple Interest Calculator
Work out simple interest on a principal over any time period.
Frequently Asked Questions
What is the simple interest formula?
Simple interest is I = P x r x t, where P is the principal, r is the annual interest rate as a decimal and t is the time in years. Interest is only ever charged on the original principal.
How is simple interest different from compound interest?
With simple interest you earn interest only on the original amount. With compound interest you also earn interest on past interest, so growth accelerates over time.
Where is simple interest used?
It is common in short-term loans, car finance, some bonds and basic savings products where the term is short and simplicity matters.
Is the Simple Interest Calculator free, and is my data private?
Yes. It is completely free and every calculation runs locally in your browser, so the numbers and dates you enter are never uploaded, stored, or shared with anyone.
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