01.06.2025

The Power of Compound Interest: Long-Term Investment in ETFs

The compound interest effect is a powerful tool for long-term investments, particularly in the form of ETFs (Exchange-Traded Funds). This effect describes how interest or returns on invested capital are earned continuously, rather than just once, leading to exponential growth. In the context of a monthly investment of €500 in an ETF, the compound interest effect can result in impressive wealth over long periods.

How Does the Compound Interest Effect Work?

The compound interest effect is based on the formula \( A = P(1 + \frac{r}{n})^{nt} \), where:

  • \( A \) is the final amount,
  • \( P \) is the principal amount,
  • \( r \) is the annual interest rate,
  • \( n \) is the number of compounding periods per year,
  • \( t \) is the number of years.

In a simple example: If you invest €1000 with an annual return of 5%, after one year you will have €1050. In the second year, not only do the original €1000 earn interest, but the additional €50 does as well, resulting in a total of €1102.50.

Application to a Monthly ETF Investment

Suppose you invest €500 monthly in an ETF with an average annual return of about 7% (which can be realistic for some ETFs). Over a long period, such as 30 years, the compound interest effect can be substantial.

Example Calculation

To understand how €500 monthly can grow to a fortune of €1,062,400, we can perform a simplified calculation:

  • Monthly Investment: €500
  • Annual Return: 7%
  • Investment Period: 30 years

Using a calculator or a formula to calculate the cumulative value of regular investments, one can determine the final amount. Such a formula might look like this:

\[ A = \sum_{i=1}^{n} P \times (1 + r)^i \]

where \( P \) is the monthly investment, \( r \) is the monthly interest rate (the annual interest rate divided by 12), and \( n \) is the number of months.

Result

When we plug in the numbers, we can see that the compound interest effect over 30 years can indeed lead to an impressive fortune. The exact amount depends on actual returns and the investment conditions.

Relevance for Private Investors

The compound interest effect offers private investors a valuable strategy for long-term wealth building. By making regular investments in ETFs, investors can benefit from the power of the compound interest effect and continuously grow their wealth. This is particularly important in a time when long-term investment strategies are gaining significance.

Tools to Support

To better understand the impacts of the compound interest effect on your investments, you can use tools like ETF savings plan calculators. These calculators allow you to simulate various scenarios and calculate the potential return on your investments over long periods. Additionally, specialized calculators like the S&P 500 ETF calculator can help analyze the historical performance of ETFs and understand the effects of regular investments.