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Simple Interest Calculator

Simple interest is charged only on the original amount, so it grows by the same sum every year. Enter the amount, the yearly rate and the time to see the interest and the total. Time can be in years, months or days.

Simple interest calculator

%
years
Time in

Days use a 365-day year.

Enter the amount, the rate and the time.

How to use it

  1. Enter amount and rate

    Type the principal (the original amount) and the interest rate per year.

  2. Enter the time

    Type how long the money is borrowed or invested, and choose years, months or days.

  3. Read the result

    See the interest, the total, and the formula used to get them.

Example: 1,000 at 5% for 3 years

Interest = 1,000 × 5% × 3 = 150.00, so the total is 1,150.00. For 6 months the interest is 25.00. For 73 days it is 10.00, because 73 ÷ 365 is one fifth of a year.

Limits and limitations

  • It does not compound. Most savings accounts and loans do, so use the Compound Interest or Loan calculators for those.
  • Days use a 365-day year. Lenders who use a 360-day year or actual days will get slightly different figures.
  • Fees, tax and repayments in stages are not included.
  • The result is an estimate for planning, not financial, tax or legal advice. Check the real figures with your lender, adviser or tax authority before you decide.

Frequently asked questions

What is the simple interest formula?

Interest = principal × rate × time, with the rate as a decimal and the time in years. The total is the principal plus the interest.

When is simple interest used?

Short-term loans, some bonds and some personal arrangements use it. Most bank accounts and long loans use compound interest.

Why is my result a few cents different from my lender's?

Lenders may count days differently, use a 360-day year or round at other steps. This tool rounds to the nearest cent once, at the end.

Is my information uploaded?

No. Your numbers is worked out by JavaScript running in your browser and is not sent to a server. The page itself still loads from a web server like any website. This site can load advertising or analytics scripts, but only after you accept them in the cookie notice. They are separate from the tools, which never pass the files or text you work with to them.

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