Simple Interest Calculator
Calculate simple interest, total repayment, and total interest earned or owed.
How this calculator works
How to use this calculator
Enter the principal amount, annual interest rate, and time period. Choose whether the time is in years, months, or days, then calculate the simple interest and total amount.
Formula used
Simple Interest = P × r × t, where P is the principal, r is the annual interest rate as a decimal, and t is the time in years. Total Amount = Principal + Interest.
Example calculation
For $5,000 at 5% annual interest for 3 years, simple interest is $750. The total amount is $5,750.
What the result means
Simple interest is calculated only on the original principal. It does not compound over time.
Frequently asked questions
Is simple interest the same as compound interest?
No. Simple interest is based only on the original principal, while compound interest also earns interest on previous interest.
Does this calculator use a 365-day year?
Yes. When days are selected, the calculator converts days into years using 365 days.
Can I use this for loans and savings?
Yes, but only when the interest is simple and does not compound.