Simple Interest Calculator
Simple interest calculator (I = P·r·t): find the interest, principal, rate or time, and the final amount.
I = P · r · t
How to use this calculator
- Choose the quantity you want under “Solve for”.
- Type the known values and pick their units: any combination works.
- The result updates as you type. Open “Show the steps” to see the substitution.
Simple interest is paid only on the original principal: I = P·r·t. It is used for many short-term loans, bonds and some savings products.
Enter the time in years or months. For interest that is reinvested, use the compound interest calculator instead.
Results are estimates for information only and do not constitute financial advice. Your lender’s or bank’s figures may differ.
Formula
I = P · r · t
| Symbol | Quantity | Units |
|---|---|---|
| P | Principal | $, €, £ |
| r | Annual interest rate | %, × |
| t | Time | years, months |
| I | Interest | $, €, £ |
Worked example
Given: P = 5,000.00 $ · r = 4 % · t = 3 years
I = P · r · t
Result: I = 600.00 $
Frequently asked questions
How much interest does $5,000 earn at 4 % for 3 years?
I = 5,000 × 0.04 × 3 = $600, for a final amount of $5,600.
What is the difference between simple and compound interest?
Simple interest never earns interest on itself; compound interest does, so it grows faster over long periods.