About this simple interest calculator
Simple interest grows only on the original principal — common in short-term loans and classroom math problems. Compare it with compound interest for long-term investing.
How to use
- Enter principal, annual rate, and time in years.
- View interest and total payable/receivable.
Formula
Interest = (P × R × T) ÷ 100 · Amount = P + Interest
Worked examples
Example: $10,000 at 6% for 3 years → interest $1,800 → total $11,800.
Tips
- For months, use T = months/12 (e.g., 18 months = 1.5 years).
Frequently asked questions
What is the simple interest formula?
I = PRT/100, where P is principal, R is annual rate percent, and T is time in years.