Your Simple Interest Summary
Interest calculated on the original principal only.
Your total amount is —, including — of simple interest.
- Principal
- —
- Annual Interest Rate
- —
- Time Period
- —
- Simple Interest
- —
- Total Amount
- —
- Formula
- I = P × R × T / 100
You earn or pay — in interest over —.
Your principal plus interest becomes —.
The original amount is —.
Interest is calculated only on the original principal, so previously earned interest does not earn additional interest.
Use simple interest when the agreement or problem specifies it. For interest-on-interest growth, use the compound interest calculator.
Finance calculations are estimates based on the values and assumptions you enter. They are not financial, tax, lending or investment advice. Verify the terms, rates, fees and local rules that apply to your situation.
About this tool
Simple Interest Calculator
A simple interest calculator using the standard principal, annual rate and time formula.
Simple Interest Calculator
Use this free simple interest calculator to calculate simple interest and the final amount from the principal, annual interest rate and time period. It works for savings, loans, classroom problems and other situations where interest is calculated only on the original principal.
Simple Interest Formula
The standard formula is I = P × R × T / 100, where P is the principal, R is the annual interest rate in percent, and T is the time in years. The total amount is A = P + I.
Example of Simple Interest
If you invest $10,000 at 6% simple interest for 3 years, the interest is $1,800 and the final amount is $11,800. The calculator performs this calculation instantly and shows the principal-versus-interest breakdown.
How to Use This Calculator
- Enter the principal amount.
- Enter the annual simple interest rate.
- Enter the time period in years.
- Select your currency if needed and choose Calculate.
- Review the simple interest, total amount, formula assumptions and visual breakdown.
Simple Interest vs Compound Interest
With simple interest, interest is calculated on the original principal throughout the selected period. With compound interest, previously earned interest is added to the balance and can earn further interest. If your financial product compounds interest, use a compound interest calculator instead.
Where Simple Interest Is Used
Simple interest is commonly used in educational examples and in some short-term lending, borrowing or savings arrangements. Actual products may use daily balances, different day-count conventions, fees or other contractual rules, so verify the applicable terms before making a financial decision.
Frequently Asked Questions
What is simple interest?
Simple interest is interest calculated directly from the original principal rather than adding previously earned interest to the interest base.
How do I calculate simple interest?
Multiply the principal by the annual rate and the time in years, then divide by 100: I = P × R × T / 100.
How do I calculate the total amount?
Add the calculated simple interest to the original principal: A = P + I.
Important Assumptions
This calculator assumes the rate is an annual simple interest rate and the time is expressed in years. It does not include taxes, fees, penalties or lender-specific accrual conventions.