Most of us would love to be a millionaire, and many of us think, often correctly, that if we want to have a comfortable retirement, we'd better be a millionaire by the time we retire. (For many others, $1 million isn't enough -- much depends on where you live and how you live.)

Here's a look at how you might become a millionaire by retirement by saving and investing just $33 per day.

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How $33 per day can get you to $1 million -- or more

An article like this can be very eye-opening and instructive, but it's hard to offer one table that applies equally well to everyone. Let's start with the table -- and I'll add a lot of caveats and considerations after it.

Data source: Calculations by author.

If you're investing $12,000 annually, that's $1,000 per month, or about $32.88 per day. It will probably be much easier to let your dollars accumulate and invest in chunks, perhaps every month or few months. (Dollar-cost averaging can be a powerful way to build wealth when you don't have a big lump sum to invest and instead will be adding money to your portfolio over time.)

I used several growth rates in that table, because the stock market can be somewhat unpredictable. Over many decades, the stock market has averaged annual returns of close to 10%. But over your investing period, it might average more -- or less.

So for best results, go ahead and aim and hope for high returns, but prepare for lower ones, just in case.

How much per day do you need to save and invest?

You'll notice that per the table, it may take you 20 or 25 years to become a millionaire, saving and investing $33 per day, on average. That might not be good enough, if you're, say, 55 years old already.

So check out the table, detailing how much you need to save to retire with $1 million -- if you want to retire at 65 and your money grows at 8% annually:

Data source: Calculations by author.

How should you invest your money?

So now that you have a rough idea of how much you should be saving and investing, how should you be investing? Well, arguably the simplest, most effective strategy is just to invest in a low-fee, broad-market index fund, such as one that tracks the S&P 500.

Since the S&P 500 has averaged annual returns close to 10% (ignoring inflation) over long periods, you have a fighting chance over your investment period to achieve an average annual gain of perhaps 8% or 10% -- or possibly more.

Index funds make investing easy, with an S&P 500 index fund, for example, such as the Vanguard S&P 500 ETF (VOO -0.25%), instantly plunking you into 500 of America's biggest companies.

If you can stomach some more risk, though, perhaps park some of your dollars in some fast-growing ETFs -- though they can be more volatile.

However you do it, be sure that you have a solid retirement plan and that you're sticking with it, saving and investing for a comfortable future.