Could Investing $400 per Month in VTI Make You a Millionaire? Here's the Math.

The Vanguard Morningstar Total Stock Market ETF (VTI -1.81%) is one of my favorite ways to invest. I own it, I believe in it, I'm buying more of it. This remarkably well-diversified exchange-traded fund (ETF) holds 3,519 stocks representing the "total" U.S. stock market.

When you invest in VTI, you don't just get the S&P 500 index. You also get a mix of thousands of other companies, including small-cap stocks, mid-cap stocks, value stocks, and more. I want to own them all, in case some of these smaller companies or undervalued sectors of the market perform better in the future.

But can investing in VTI really make you a millionaire? Actually, yes. It can. Let's look at historical returns for this total stock market ETF and see how much you could earn.

Example 1: $400 a month in VTI earning 9.38% annualized returns

VTI has a long track record. This fund was established in May 2001. Over the past 25 years, it's delivered average annual returns of 9.38%. Future returns are not guaranteed, but let's assume that you could earn that same return for the next 25 years or more.

If you invested $400 a month in the VTI, earning 9.38% annualized returns, in five years, your investment would grow to $28,945. After 10 years, you'd have $74,262. After 20 years, you'd have $256,293. After 30 years, you'd have $702,488. And in year 34, you'd pass the million-dollar mark -- your investment would now be worth about $1.028 million.

Example 2: $400 a month in VTI earning 10.95% annualized returns

What if VTI can deliver stronger returns and get you to millionaire status faster? Over the past five years, this fund has delivered 10.95% annualized returns.

Let's assume you invested $400 per month in VTI and the fund maintained its 10.95% average annual return. After 10 years, you'd have $80,073. After 20 years, you'd have $306,410. After 30 years, you'd have $946,190. And in year 31 you'd become a millionaire, with more than $1.05 million.

Example 3: $400 a month in VTI earning 14.87% annualized returns

Over the past 10 years, VTI delivered even stronger annualized returns: 14.87%. There's no guarantee that such a strong return will keep coming forever. But let's assume you can earn that higher return on your VTI investments -- this rate of return could make you a millionaire even faster.

If you invested $400 a month in VTI, earning an average annual return of 14.87%, after 10 years you'd have $96,841. After 20 years, you'd have $484,211. And after 25 years of investing in VTI, you'd be a millionaire: $1,000,709.