The power of compounding grows your savings faster

How compound interest works

Compound interest is the interest you get on:

the money you initially deposited, called the principal
the interest you've already earned

For example, if you have a savings account, you'll earn interest on your initial savings and on the interest you've already earned. You get interest on your interest.

This is different to simple interest. Simple interest is paid only on the principal at the end of the period. A term deposit usually earns simple interest.

Save more with compound interest

The power of compounding helps you to save more money. The longer you save, the more interest you earn. So start as soon as you can and save regularly. You'll earn a lot more than if you try to catch up later.

For example, if you put $10,000 into a savings account with 3% interest compounded monthly:

After five years, you'd have $11,616. You'd earn $1,616 in interest.
After 10 years you'd have $13,494. You'd earn $3,494 in interest.
After 20 years you'd have $18,208. You'd earn $8,208 in interest.

Use the compound interest calculator

Work out how much you can earn in interest if you start saving now.

Compound interest formula

To calculate compound interest, use the formula:

A = P x (1 + r)ⁿ

A = ending balance
P = starting balance (or principal)
r = interest rate per period as a decimal (for example, 2% becomes 0.02)
n = the number of time periods

How to calculate compound interest

To calculate how much $2,000 will earn over two years at an interest rate of 5% per year, compounded monthly:

1. Divide the annual interest rate of 5% by 12 (as interest compounds monthly) = 0.0042

2. Calculate the number of time periods (n) in months you'll be earning interest for (2 years x 12 months per year) = 24

3. Use the compound interest formula

A = $2,000 x (1+ 0.0042)²⁴
A = $2,000 x 1.106
A = $2,211.64

Case Study

Lorenzo and Sophia compare the compounding effect

Lorenzo and Sophia both decide to invest $10,000 at a 5% interest rate for five years. Sophia earns interest monthly, and Lorenzo earns interest at the end of the five-year term.

After five years:

Sophia has $12,834.
Lorenzo has $12,500.

Sophia and Lorenzo both started with the same amount. But Sophia gets $334 more interest than Lorenzo because of the compounding effect. Because Sophia is paid interest each month, the following month she earns interest on interest.

Source : MoneySmart. gov.au May 2020

Reproduced with the permission of ASIC’s MoneySmart Team. This article was originally published at https://moneysmart.gov.au/saving/compound-interest

Important note: This provides general information and hasn’t taken your circumstances into account. It’s important to consider your particular circumstances before deciding what’s right for you. Although the information is from sources considered reliable, we do not guarantee that it is accurate or complete. You should not rely upon it and should seek qualified advice before making any investment decision. Except where liability under any statute cannot be excluded, we do not accept any liability (whether under contract, tort or otherwise) for any resulting loss or damage of the reader or any other person. Past performance is not a reliable guide to future returns. Important Any information provided by the author detailed above is separate and external to our business and our Licensee. Neither our business nor our Licensee takes any responsibility for any action or any service provided by the author. Any links have been provided with permission for information purposes only and will take you to external websites, which are not connected to our company in any way. Note: Our company does not endorse and is not responsible for the accuracy of the contents/information contained within the linked site(s) accessible from this page.

Back to front page