Simple interest calculator
Simple interest applies each period’s rate to the original principal. Enter a rate and duration using matching time periods.
Calculate simple interest
Formula
J = C × i × t, where C is principal, i is the rate per period as a decimal, and t is the number of periods. Final amount = C + J.
Limits
This is a mathematical simulation. It excludes fees, taxes, inflation, contract terms and currency conversion. The rate and duration must use the same period; for example, a monthly rate with a number of months.
Frequently asked questions
What does 2% per month for 12 months mean?
In the simple-interest model, each month applies 2% to the original principal. On 1,000 units, that gives 240 units of interest and a total of 1,240, before any fees or other terms.
Can I enter an annual rate?
This calculator applies the rate once per period. Match the period to the rate you enter; an effective annual rate is not necessarily converted by simply dividing by 12.
Do all loans use simple interest?
No. Methods and terms vary by product and contract. Check the applicable documents for the rate, period, fees and calculation method.