Simple Interest Calculator
Calculate interest earned or owed using the simple interest formula.
Interest
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Usage examples
Estimating interest on a savings account
Enter the amount, rate, and term of a simple-interest savings product to see the interest you'll earn at maturity.
Comparing short-term loan costs
Calculate the simple interest on a loan measured in days or months to compare different loan offers.
Checking a textbook finance problem
Quickly verify the answer to a simple interest problem from a finance course.
Frequently asked questions
What's the difference between simple and compound interest?
Simple interest is calculated only on the original principal, while compound interest also earns interest on previously accumulated interest. If you need compound interest, use this site's compound interest calculator instead.
How is time handled when entered in days?
The calculator assumes 365 days per year and converts your input into years before applying the formula. It doesn't account for leap years or other calendar details.
If I switch the time unit, does my entered number change?
Yes. For example, if you enter 24 months and then switch to years, the value automatically converts to 2 — the underlying time is preserved, not just relabeled.