Very random number, I know. But there’s a good reason for that.

Using a stock performance calculator and leveraging the power of math and statistical analysis, this is the number you’ll have after 25 years if you start with $100 in stock and continue contributing $200 a month.

The main idea of investing is to end up with more money than you started with. The difference between what you earn or lose is called your “return on investment.” The cool part is, the longer you keep your money invested, the more you can make because of something called compounding returns. Albert Einstein famously called this concept the 8th wonder of the world.

There are online calculators specifically designed for stock investments (among other areas) to help you figure out how much your investment might grow over time. My favorite is Nerd Wallet’s investment calculator, which you can use for free here.

How to use the investment calculator:

Start with what you have. If you’ve got $100 to invest right now, put that number in like my example. If you don’t have any money to start with, just enter $0.

Add what you’ll put in regularly. If you plan to add a certain amount every month (this is called dollar-cost averaging and yes, you should definitely do this), put this number in after choosing the “monthly” option. If you want to add a big amount once a year instead, pick “annually” and write down how much you’ll contribute each year.

Put in a realistic number. Even a small contribution will help greatly!

Decide how long to keep your money in. Think about how long you want to stay invested. For stocks, it’s usually smart to stay in for at least five years to get through any ups and downs.

Guess your earnings rate. As an example, the S&P 500 usually goes up by about 10% a year on average, but this doesn’t mean it will happen every year. Some years you might earn more, some less. Over time, you hope to average out to a good amount of profit. We use a 7% return rate as a starting point because it’s pretty cautious. You can change this to what you think your investments will actually do.

Choose how often your investment grows. You can have your investment grow at the same time as you make contributions, like monthly or yearly. But choosing monthly growth can give you a closer idea of what to expect from real investments, since growing your investment more often usually means more money over time.

You can use the free online calculators at Nerd Wallet or Smart Asset, and there are others as well. Play with this calculator! This way, you can get a better idea of how your investment might increase over the years. The tiniest of changes can butterfly effect it’s way to huge differences in the long run.

This is basically time travel! The ability to see future outcomes is incredible with these calculators. It brings clarity to the cloudy world of investments. It should be noted that these calculators use math and statistics, so it can only give a rough estimated guesstimate. But this is how smart people get rich, by maximizing the potential of what they have and using math to their advantage.

Don’t worry if you don’t understand the math involved. You don’t have to! That’s what these calculators do. You can research what numbers it’s using if you’d like. It’s quite fascinating.

Turning a modest $100 into a staggering $162,587.88 over 25 years might seem like a magic trick, but it’s all based on the solid principles of investing and the “miracle” of compounding returns. This example isn’t just a showcase of numbers; it’s a powerful illustration of how starting small, staying consistent, and making informed choices can lead to substantial growth over time.

Whether you’re a seasoned investor or just starting out, the journey to financial growth begins with understanding and leveraging the tools available to you, such as investment calculators. These tools not only demystify the process but also empower you to make decisions that can turn your financial goals into reality. One final note: Try the other calculators on Nerd Wallet, especially the retirement ones.