BYTETOOLS

Simple Interest Calculator

Calculate simple interest with the I = P × r × t formula. Enter principal, annual rate and time to see the interest and total amount instantly.

$750.00
Simple interest
$5,750.00
Total amount (P + I)

Formula used

I = P × r × t = 5,000 × 5% × 3 = $750.00

Estimates only, not financial advice. Simple interest does not compound.

  • Uses the standard I = P × r × t formula
  • Shows both the interest and the total amount
  • Displays the worked formula for transparency
  • Accepts fractional years for short-term loans
  • Any currency symbol, no live exchange rates
  • Private, in-browser calculation; estimates only

How to use the Simple Interest Calculator

  1. 1

    Select your currency symbol.

  2. 2

    Enter the principal amount (P).

  3. 3

    Enter the annual interest rate as a percentage (r).

  4. 4

    Enter the time period in years (t).

  5. 5

    Read the simple interest and the total amount, with the formula shown.

About the Simple Interest Calculator

The ByteTools Simple Interest Calculator applies the classic formula I = P × r × t to work out the interest on a loan or deposit. Enter the principal, the annual interest rate and the time in years, and it instantly returns the interest earned or owed plus the total amount (principal + interest).

Simple interest is common for short-term loans, car finance, bonds and back-of-the-envelope estimates where interest does not compound. This tool is handy for students learning the formula and anyone who wants a quick, transparent calculation.

All math runs locally in your browser, so nothing is uploaded. Figures are estimates for planning only and are not financial advice.

Frequently asked questions

What is the simple interest formula?

Simple interest uses I = P × r × t, where P is the principal, r is the annual interest rate as a decimal and t is the time in years. The total amount you repay or receive is the principal plus that interest, A = P + I.

When is simple interest used instead of compound interest?

Simple interest is common for short-term personal loans, some car loans, treasury bills and bonds where interest is paid out rather than reinvested. It never earns interest on interest, so it is easier to calculate and slightly cheaper for borrowers than compound interest.

How do I calculate simple interest for months?

Convert the months into a fraction of a year and enter that as the time. For example, 6 months is 0.5 years and 3 months is 0.25 years. The calculator accepts decimals, so you can enter these directly.

Does this calculator compound the interest?

No. This tool deliberately uses simple interest, which is charged only on the original principal. If you want interest that earns its own interest each period, use a compound interest calculator instead.

Is my data kept private?

Yes. The calculation happens entirely in your browser and nothing is transmitted or saved. You can use it on confidential figures without any privacy concerns.

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