How is simple interest calculated?

It uses SI = P x R x T / 100, where P is the principal, R is the annual rate and T is the time in years.

How is it different from compound interest?

Simple interest is charged only on the original principal, while compound interest is charged on the principal plus previously accrued interest.

Can I use months for the time?

Yes. Choose months and the calculator converts the period to years before applying the formula.

Finance Calculators

Simple Interest Calculator

Calculate simple interest and the total amount from principal, rate and time.

Free browser toolRuns in your browserNo sign-up

PrincipalCurrencyAnnual interest rate (%)

TimeUnit

Simple interest

$1,800.00

Interest

$11,800.00

Total amount

Simple interest uses SI = P x R x T / 100. Interest is charged only on the original principal, so it does not compound over time.

Simple interest formula explained

Simple interest is calculated only on the original principal, so the interest charge stays constant for every equal period.

SI = P x R x T / 100; Total = P + SI

P: Original principal
R: Annual rate as a percentage
T: Time in years

Worked example

$10,000 at 6% for 3 years earns $1,800 interest, producing a total of $11,800.

Practical tips

Match the time unit
Convert months to years before applying an annual rate.
Check the interest method
Loans and deposits may use compound or reducing-balance interest instead.

About the Simple Interest Calculator

The Simple Interest Calculator finds the interest charged on a principal using SI = P x R x T / 100, along with the total amount owed or earned.

Simple interest is calculated only on the original principal, so it does not compound. This makes it common for short-term loans and some fixed deposits.

You can enter the time in years or months, and every calculation runs entirely in your browser.

Key features

Simple interest and total amount
Time in years or months
Locale-aware currency formatting
Instant browser-based calculation

How to use

1Enter the principal and choose a currency.
2Enter the annual interest rate.
3Enter the time and choose years or months.
4Read the simple interest and total amount.

Examples

Simple interest

Input: Principal 1000, rate 5%, 2 years

Output: Interest 100, total 1100

Interest is principal x rate x time, with no compounding.

Frequently asked questions

How is simple interest calculated?: It uses SI = P x R x T / 100, where P is the principal, R is the annual rate and T is the time in years.
How is it different from compound interest?: Simple interest is charged only on the original principal, while compound interest is charged on the principal plus previously accrued interest.
Can I use months for the time?: Yes. Choose months and the calculator converts the period to years before applying the formula.

Open a related tool to prepare your files or refine the finished result.