This simple interest calculator estimates interest that accrues only on the original principal.
Finance
Simple Interest Calculator
Calculate simple interest and total amount from principal, rate and time.
Calculator
About this calculator
Formula notes
Simple interest is commonly I = P x r x t, and the total amount is P + I.
Worked examples
- Example: 10,000 at 5% for 2 years produces about 1,000 in simple interest, for a total near 11,000.
- A principal of $7,500 at 4.2% simple annual interest for 18 months earns $472.50, giving a final amount of $7,972.50.
How to use it
- Enter principal, rate, and time.
- Confirm whether time is measured in years or another unit supported by the form.
- Read the interest and total amount.
Frequently asked questions
When is simple interest used?
It appears in some short-term loans, teaching examples, and simplified finance estimates.
When is simple interest commonly appropriate?
It fits problems where interest is calculated only on the original principal for the entire term. Confirm the actual contract method.
Limits and interpretation
- Simple interest does not add earned interest to principal, so it is unsuitable for accounts or debts that compound.
- Day-count conventions, fees, payment timing, and changing principal can make real contract interest differ from P x r x t.