What is a simple Interest Calculator?
Simple interest is calculated only on the original principal for the entire period — unlike compound interest, previously-earned interest never itself earns further interest. It shows up in specific contexts like some personal loans, certain post office schemes, and back-of-envelope interest estimates, though most everyday savings and investment products actually use compound interest instead.
Enter the principal, rate and time period to see the interest and total amount payable or receivable.
How simple interest is calculated
Rate is the annual percentage rate and Time is in years. Because the base for interest never changes, simple interest grows in a straight line over time, unlike the accelerating curve of compound interest.
Frequently asked questions
When is simple interest actually used?
It shows up in some personal and short-term loans, a handful of specific post office schemes, and it’s the standard convention for calculating things like SCSS or Post Office MIS quarterly/monthly payouts, which don’t reinvest interest back into the principal.
Simple or compound — which gives a higher return for a saver?
For the same nominal rate, compound interest always earns more over time than simple interest, because it earns "interest on interest." The gap widens the longer the money stays invested.
Can Time be a fraction of a year?
Yes — enter it as a decimal (e.g., 0.5 for 6 months, 0.25 for 3 months) and the calculator will prorate accordingly.