How to calculate simple interest in 3 easy steps
- 1
Enter the principal
The amount borrowed or invested.
- 2
Set the rate and time
Annual interest rate in percent, and the duration in years.
- 3
Read the result
Interest earned and the total amount (principal + interest) appear instantly.
Why use the simple interest calculator tool from Super Utility Hub?
Simple interest is charged only on the original principal — no interest on interest. That makes it predictable and easy to verify by hand, which is why it is standard for short-term loans, promissory notes, and some bonds.
Enter the principal, the annual rate, and the time in years to see the interest earned, the total amount, and the equivalent monthly interest.
- Processes everything in your browser — no upload servers involved
- Free forever with unlimited uses
- Works on Windows, macOS, Linux, Android and iOS
- No watermark or branding on your output, ever
Frequently asked questions
How is simple interest different from compound interest?
Simple interest is computed on the original principal only. Compound interest also earns on previously accrued interest, so it grows faster over time.
What is the formula?
Total = P × (1 + r × t), where P is the principal, r the annual rate as a decimal, and t the time in years.
When is simple interest used?
Short-term consumer loans, car loans in some countries, promissory notes, and certain bonds. Mortgages and credit cards compound.