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What is Compound Interest?

Understanding Compound Interest

Compound interest is an extremely powerful concept that can greatly impact your savings, investments, and debt. It refers to the interest earned not only on the principal amount but also from the accumulation of interest from previous periods.

Compound Interest vs. Simple Interest

Compound interest differs from simple interest, which is calculated solely on the principal loan amount. With compound interest, the interest is calculated on the principal amount and any accumulated interest. With savings and investments, the interest earned is reinvested (compounded), allowing your savings or investments to grow over time.

Simple interest is typically used for short-term loans, while compound interest is used for long-term investments and loans.

The Power of Compounding Interest

Compound interest has the potential to greatly multiply your money over time, significantly impacting the growth of your savings and investments.

The interest earned is on both the principal and the accumulated interest, it basically generates “interest on interest.” This means that not only does the initial principal amount earn interest, but the interest earned also earns interest, leading to exponential growth.

Compounding Frequency

The frequency of compounding can vary, daily, monthly, quarterly, semiannually, annually, or even continuous compounding. The more frequent the compounding periods, the more rapidly your principle balance grows.

When looking at different savings and investment vehicles, it is important to evaluate what the frequency of compounding is, as this can lead to faster money growth.

The Benefit of Compounding on Savings

Compound interest is extremely advantageous for savings accounts. For example, if your savings account earns 4% interest annually, the interest is added to the principal balance once per year. However, if the interest is compounded monthly, the 4% annual interest is divided by 12, and added to the principal balance 12 times per year.

Therefore, choosing a savings account with higher interest rates and more frequent compounding will maximise your returns.

Compounding Interest on Debt

While compound interest can work in your favour for savings, it can have the opposite effect on debt. When interest is compounded on debt, the interest is added to the principal balance. This can result in the debt quickly spiralling out of control and becoming more difficult to pay off.

For example, if a borrower has a credit card with a high interest rate and only makes the minimum monthly payments, the interest on the debt will be compounded, and the debt will grow more quickly over time, resulting in the borrower paying much more for the loan.


Understanding compound interest will help you to make a more informed choice about your savings, investments, or debt.

With debt, it is best to pay it off as quickly as possible, minimising the impact of compound interest and saving money in the long run. In contrast, choosing the right investment or savings vehicle, and taking advantage of compounding will allow you to harness compound interest’s immense power to grow your wealth exponentially over time.