Want to become a millionaire before retirement? Chances are good this goal is within reach, even if you don't have a huge income. But, you'll need to start investing ASAP to grow a seven-figure nest egg because you need time for your money to grow.

So, how much do you need to save to become a millionaire in your later years? The amount depends on when you begin investing. 

Person sitting in front of computer and laptop looking at investment information.

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Here's exactly how much you need to save to become a millionaire

To see the monthly amount you must save to become a millionaire, check out the table below. The estimated amounts are based on earning an average of 8% annual returns, which is a reasonable return on investment (ROI) to expect if you have a balanced portfolio of stocks and bonds. 

Years to Invest How Much to Save Monthly to Become a Millionaire
5 $14,204.68
10 $5,752.44
15 $3,069.12
20 $1,821.01
25 $1,139.89
30 $735.61
35 $483.60

Table calculations: Author.

The table makes one thing very clear: Investing earlier means you won't have to save nearly as much money each month in order to become a millionaire. That's not just because you're putting more money away over time; it's because the money you have invested can start working for you earlier. It earns returns, which can be reinvested. Eventually your money is making a lot of money for you, even without any additional contributions. 

Now, if you can't afford to put this much aside, it's still best to start saving something. Investing even a little bit when you're younger can help you get started in growing your nest egg so you won't have to contribute as much later to become a millionaire, since you won't be starting from $0. 

How can you hit your savings targets? 

Once you know how much to invest to become a millionaire, the key is to save that amount consistently each and every month. 

The easiest way to do this is to make the process automatic. Start by setting a budget and prioritizing investing for your future as a must-pay bill. By building the rest of your budget around your retirement investing, you can make sure the discretionary spending you do doesn't prevent you from hitting your million-dollar target. 

After you've made sure you can afford to save the requisite amount, arrange to have the funds transferred over to your investment account on a monthly basis. You can have the money taken out before you get your paycheck if you're investing in a 401(k). If you're putting money into another type of account, such as an IRA, you can arrange an automated transfer on payday. 

After automating the process, just leave the money alone and don't change your contributions unless you're increasing them. Make sure you're investing in a good mix of assets so you can maximize the chances of earning the necessary 8% returns. Then, sit back and watch your money grow until you become a millionaire.