Saving for retirement is tough, but you don't need to be a stock market expert to make a lot of money. You also don't need to be rich to generate wealth by investing -- you just need the right strategy.

Not all investments are created equal, and some options are stronger than others. If you're looking for a low-maintenance investment that could make you a lot of money over time, there's one exchange-traded fund (ETF) that stands out: The S&P 500 ETF.

The S&P 500 ETF: What you need to know

An S&P 500 ETF is a fund that includes all the stocks within the S&P 500 index itself, and it aims to match the index's performance over time.

This ETF is perfect for those who want to invest but don't want to spend countless hours researching companies and individual stocks. Because the stocks within the S&P 500 are from some of the largest and strongest businesses in the U.S., this ETF is both a powerhouse and a relatively safe investment.

The S&P 500 itself has weathered dozens of crashes, corrections, bear markets, and recessions over the years. Despite all the volatility, however, it's earned positive average returns over the long run.

Chart showing overall upward trend of the S&P 500 since 2000.

^SPX data by YCharts

That makes this type of investment especially smart for those looking to minimize their risk during periods of economic uncertainty. Regardless of what the future may hold, it's almost guaranteed that the S&P 500 will recover -- and so will your investments.

How much can you earn?

While the S&P 500 is one of the safer investments out there, it's also possible to make a lot of money. With the right strategy, you could potentially earn well over $1 million by the time you retire.

Historically, the S&P 500 has earned average annual returns of roughly 10% over time. In other words, all the ups and downs it experiences from year to year have averaged out to around 10% per year over the long run.

Say, for example, you want to accumulate at least $1 million by retirement age. Assuming you're earning a 10% average annual return, here's approximately how much you'd need to invest each month depending on the number of years you have left to save.

Number of Years Amount Invested per Month Total Savings
40 $200 $1.062 million
35 $325 $1.057 million
30 $525 $1.036 million
25 $900 $1.062 million
20 $1,500 $1.031 million

Source: Calculations by author via

The more time you have to let your money grow, the less you'll need to invest each month to reach your goal. If you haven't already started investing, then, now is the time to jump in.

What if you're falling behind?

If you don't have decades to build your retirement fund, that's OK. If you can swing it, investing more per month can help you save more money in a shorter amount of time.

Regardless of how much you can afford to invest or how many years you have until retirement, though, it's wise to start saving now. Even if you're falling behind, it's still possible to save hundreds of thousands of dollars with an S&P 500 ETF.

It's never too late to start investing, and S&P 500 ETFs are a smart option for many people. By investing as much as you can afford and giving your money as much time as possible to grow, you'll be well on your way to retiring a millionaire.