What Is Compound Interest?

Compound interest (or compounding interest) is the interest on a loan or deposit calculated based on both the initial principal and the accumulated interest from previous periods. Thought to have originated in 17th-century Italy, compound interest can be thought of as “interest on interest,” and will make a sum grow at a faster rate than simple interest, which is calculated only on the principal amount.

The rate at which compound interest accrues depends on the frequency of compounding, such that the higher the number of compounding periods, the greater the compound interest. Thus, the amount of compound interest accrued on $100 compounded at 10% annually will be lower than that on $100 compounded at 5% semi-annually over the same time period. Because the interest-on-interest effect can generate increasingly positive returns based on the initial principal amount, compounding has sometimes been referred to as the “miracle of compound interest.”

Let’s look at a hypothetical example. Pretend you have $5,000 in a retirement account, earning 7% interest each year. The first year that your account is open, you earn $350 in interest, which brings your total to $5,350. The following year, interest is calculated based on that $5,350 total, not the original $5,000. You earn $374 in interest and now have a total of $5,724.

Even if you never deposit anything but the original $5,000, you’ll have $38,061.28 in 30 years. That’s a $33,061.28 profit.

Compound interest rewards people who invest over long periods of time, not necessarily those who can afford to invest the most. It’s specifically helpful for young people who start investing early.

A 25-year-old who invests $200 a month with 7% interest will have $226,705.89 in 30 years. If they wait 10 years to start investing, they’ll have to more than double their savings rate to reach the same total.

Pros and Cons of Compound Interest

Compound interest is your best friend when you’re investing or saving for a long-term goal, but it’s your worst enemy if you have debt that’s not being paid off.

Here’s an example: A borrower with $30,000 in student loans defers their loans for a year while they look for a job. During that year, interest continues to accrue on those loans. Once they’re ready to resume making payments, they discover their $30,000 balance has grown to $45,000 because of compound interest.

To slow down the negative effects of compound interest, you should pay off your debt as quickly as possible. You can also refinance your loans to a lower interest rate. When you borrow money, compounding interest works against you and benefits the lenders. The interest rate a lender charges is the trade-off for taking on the risk of lending money and giving out loans. However, it makes it very important for you, the borrower, to pay off your loans on time and keep tabs on your interest rate.

Compound Interest Investments

Compounding interest investment accounts can help both grow your money and secure your future. But it’s important to start early. And before you start investing in stocks, it’s important not to get ahead of yourself. Do your research and familiarize yourself with different investment options. Make sure you’re only investing money after you’ve topped off your emergency fund. It’s also important to ensure that you’re current on all your loan payments. Otherwise, any investment gains might be negated by snowballing debts.

If you’re saving for retirement, invest in low-fee index funds. Fees of 1% or more will drag down your profit and cut into your compound interest. Index funds will follow the market’s course and provide a solid rate of return. Avoid investing in individual stocks, as their volatility can be problematic.

Compound interest works best if you start saving as soon as possible, even if it’s just $25 a month. A 22-year-old who saves $25 a month at 7% interest for five years will have $1,795.80. When she gets a raise after those five years and can afford to put away $100 a month, she’ll have $294,213.07 when she retires at age 67. If she hadn’t started investing until after her raise, she’d only have $264,689.70.

Even though she only contributed $1,500 during those first five years, her portfolio is worth nearly $30,000 more. For most people, that’s enough to retire a full year earlier, and all it cost her was a monthly contribution of $25. Even someone earning an entry-level salary can afford that.

The same principle applies to debt. Even if you defer your student loans, keep making payments on them as much as you can afford to. Taking time off will only delay your debt payoff and increase how much you pay in interest.

Always compare rates before taking out a loan and get at least three quotes. Each percentage point matters when you’re borrowing money, especially for long-term debt like a mortgage. You can also limit compound interest by borrowing money for as little time as possible.

Takeaways: The Power of Compounding Interest and Growing Your Wealth.

Compound interest can help you grow your wealth and secure a more stable financial future. Even if you can’t afford a large principal or large ongoing additions to your investment, you can still extract value from small investments with compounding interest. The key is to start as early as possible and do adequate research to ensure that you’re making investment decisions that make sense with your overall financial goals and situation. With these tips, you’ll be on your way to stabilizing your financial foundation and making your money work for you.