Simple Interest Calculator

Calculate simple (non-compounding) interest on a principal over time, the interest earned and the total amount, using I = P · r · t.

Interest earned

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Principal-
Total amount-

Show the math

Simple interest is charged only on the original principal:

I = P · r · t

P = principal · r = yearly rate · t = time in years. Unlike compound interest, nothing is earned on previously earned interest, so the total is simply principal plus interest. Use decimals for partial years (0.5 = six months).

What this does

A simple interest calculator finds the interest earned on a principal over time with no compounding. It returns the interest and the total amount using the formula I = P · r · t.

How it works

Simple interest is charged only on the original principal, not on accumulated interest, so it grows in a straight line. Here P is the principal, r is the annual rate, and t is the time in years. It is common for short-term loans and some bonds.

I = P · r · t

How to use it

  1. Enter the principal amount.
  2. Enter the annual interest rate.
  3. Enter the time in years (decimals allowed).
  4. Read the interest earned and the total amount.

Understanding your result

Because nothing compounds, simple interest is lower than compound interest over the same period, a useful quick baseline rather than a growth projection.

Example

$5,000 at 4% for 3 years earns $600 in simple interest, for a total of $5,600.

Sources & methodology

Last updated .

Frequently asked questions

What is simple interest?

Simple interest is charged only on the original principal, not on accumulated interest. The formula is I = P · r · t, where P is the principal, r is the yearly rate, and t is the time in years.

How is it different from compound interest?

Compound interest also earns interest on previously earned interest, so it grows faster. Simple interest is common for short-term loans and some bonds where no compounding occurs.

Can I use a partial year?

Yes, enter the time in years, including decimals (for example 0.5 for six months).

Is anything saved?

No. All math happens in your browser; nothing you type leaves your device.