Simple Interest Calculator
Compute simple interest with the formula I = P × r × t.
A quick simple-interest calculator. Enter principal, annual rate and time in years to see the interest accrued and the total amount.
Common use cases
- Calculate interest on short-term personal loans
- Compute basic bond coupon payments
- Estimate interest on a fixed-deposit before tax
- Compare simple vs compound interest for math homework
Frequently asked questions
Simple vs compound interest?▾
Simple interest accrues only on the principal; compound interest accrues on principal + previously earned interest.
What's the formula?▾
I = P × r × t, where r is the annual decimal rate and t the time in years.
Can t be a fraction?▾
Yes — enter 0.5 for six months or 0.25 for three months.