About the Simple Interest Calculator
Simple interest is charged only on the original principal — common for short-term loans, some bonds, car loans in certain states and promissory notes. The formula is I = P × r × t; enter time in years, months or days.
How to use it
- Enter principal and annual rate.
- Enter the time and its unit.
- Read the interest and total amount.
Good to know
- Results are estimates for planning purposes and not financial, tax or legal advice. Lenders and tax authorities may calculate differently.
- Day counts use a 365-day year. Some lenders use 360 days (“banker's year”), which slightly increases interest.