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Simple Interest Calculator

Calculate simple interest on a deposit or loan. Interest is charged only on the original amount, so it grows by the same amount every period.

Interest–
Total amount–

For general information only. Results are estimates based on the numbers you enter and are not financial advice. Actual figures from a bank or lender may differ because of fees, rounding or payment timing.

How to use the Simple Interest Calculator

  1. Enter the principal, the yearly interest rate and the time period.
  2. Choose years or months for the time.
  3. Read the interest and the total amount.

The formula

Simple interest = P × R × T ÷ 100, where P is the principal, R is the annual rate in percent and T is the time in years. The total amount is the principal plus the interest. If the time is entered in months, it is divided by 12 first.

Worked example

5,000 at 6% for 3 years earns 5,000 × 6 × 3 ÷ 100 = 900 in interest, so the total is 5,900. For 18 months at the same rate, T = 1.5 and the interest is 450.

Simple versus compound interest

With simple interest the amount earned each year stays the same. With compound interest, earlier interest is added to the balance and also earns interest, so growth speeds up over time. Use our compound interest calculator to compare the two.

Frequently asked questions

What is simple interest?

Interest calculated only on the original principal, not on interest already earned.

What is the simple interest formula?

Interest = Principal × Rate × Time ÷ 100, with the rate in percent per year and time in years.

Where is simple interest used?

Some short-term loans, certain bonds and many classroom problems use simple interest. Most savings accounts and long-term loans use compounding instead.

Can I enter the time in months?

Yes. Select Months and the calculator converts the time to years for you.

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Compound Interest CalculatorFree compound interest calculator with optional monthly deposits. See your final balance, interest earned and year-by-year growth.Loan EMI CalculatorFree loan EMI calculator. Enter the amount, interest rate and term to see your monthly payment, total interest and a yearly repayment schedule.Percentage CalculatorFree percentage calculator: find X% of a number, what percent one number is of another, and percentage increase or decrease.

Last updated: November 6, 2026