Simple Interest calculator.
Use this free simple interest calculator to get fast estimates, compare scenarios, and understand the numbers with clear step-by-step context.
Use the Simple Interest Calculator.
Results update automatically as you type. No account is required.
Enter the loan or deposit
Amount
The principal you borrow, lend, or deposit.
Rate and time
Simple interest is charged only on the principal, not on accrued interest.
$5,000 at 4% simple interest for 10 years earns $2,000.
Value over time
Principal plus interest grows in a straight line.
Principal vs. interest
How much of the total is interest.
About the Simple Interest Calculator
The simple interest calculator works out the interest on a principal amount when interest is charged only on the original sum — not on previously earned interest. Simple interest is common on some short-term loans, car loans, and bonds, and it is the easiest interest model to understand. Enter a principal, an annual rate, and a time in years to see the interest and the total value.
How simple interest is calculated
Simple interest uses I = P × r × t, where P is the principal, r is the annual rate as a decimal, and t is the time in years. The total amount is the principal plus the interest. Because interest is not added back to the balance, the value grows in a straight line rather than the accelerating curve of compound interest.
Simple interest vs. compound interest
With simple interest you earn or pay the same amount each year. With compound interest, interest itself earns interest, so the total grows faster over time. For short periods the difference is small, but over many years compound interest pulls far ahead — which is why long-term savings usually use compounding.
Using the result
Use this to check the cost of a simple-interest loan or the return on a fixed deposit. The chart shows the steady, linear growth that distinguishes simple interest from compounding.
Important disclaimer
⚠ Disclaimer: This simple interest calculator is for general education and planning only and is not financial advice. Many real loans and savings products use compound interest or additional fees, so confirm the exact terms with your lender or institution.
Related calculators
Compound Interest Calculator · Future Value Calculator · Loan Calculator · Savings Calculator
Simple Interest Calculator FAQ
What is simple interest?
Simple interest is interest calculated only on the original principal, using I = P × r × t. It does not earn interest on previously accrued interest.
How do I calculate simple interest?
Multiply the principal by the annual rate (as a decimal) and by the number of years. For example, $5,000 at 4% for 10 years is $5,000 × 0.04 × 10 = $2,000 of interest.
What is the difference between simple and compound interest?
Simple interest is charged only on the principal, so it grows in a straight line. Compound interest is charged on the principal plus accumulated interest, so it grows faster over time.
Where is simple interest used?
It is common on some car loans, short-term personal loans, and certain bonds and fixed deposits, where interest does not compound.
Does simple interest grow in a straight line?
Yes. Because the same interest is added each year, the total value increases linearly, which the chart shows clearly.
Is this simple interest calculator free?
Yes. It is free, needs no sign-up, and runs entirely in your browser.