A million dollars just doesn't go as far as it used to. According to an August 2023 Charles Schwab survey, U.S. workers surveyed now believe that they'll need $1.8 million to retire — and just 37% of respondents believe they can reach this goal.

So how much do you need to invest each month to have $1.8 million for retirement? CNBC Select crunched the numbers and broke it all down by age group.

When it comes to investing, the three most important factors to consider are time horizon (how long you have to invest before your desired retirement date), yearly return and the amount you contribute each month or year.

The longer you plan to keep your money in the market, the more time it has to grow. This is why financial experts recommend starting to invest as early as possible. Plus, when you start investing at a younger age, you can contribute smaller amounts each month and still reach the same goal.

Often, your yearly return may depend on how risky of an asset you've decided to invest in. Riskier investments (such as individual stocks) usually have the potential to give higher returns than safer assets such as exchange-traded funds (ETFs) or mutual funds. Of course, though, all investments carry some degree of risk.

Your risk tolerance can give you some indication of what kinds of assets you should invest in. Robo-advisors like Betterment and Wealthfront use your risk tolerance, among other factors like time horizon and financial goals, to recommend portfolios for you to invest in. And, these platforms automatically adjust the way your money is allocated over time to continue fitting your goals.

With the time horizon, monthly contribution and yearly return in mind, you can simply use one of the many online investment calculators to figure out how much of a balance you'd have in a certain amount of time. If you use the calculator.net tool, which is what we used to determine calculations in the next section, you can input your end goal and figure out exactly how much money you need to invest each month to reach that goal.

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Below, we did the math to figure out how much money individuals in their 20s, 30s, 40s and 50s would need to save each month to reach $1.8 million by age 65. We calculated each scenario with a diverse array of yearly returns: 3%, 6% and 9%. These calculations also assume your starting amount is $0.

How much 25-year-olds should invest each month to have $1.8 million:

• At a 3% yearly return, 25-year-olds would need to invest $1,962.52 a month for 40 years to reach $1.8 million.
• At a 6% yearly return, you'd need to invest $943.56 a month for 40 years to reach $1.8 million.
• At a 9% yearly return, you'd need to invest $426.62 a month to reach the same goal.

How much 30-year-olds should invest each month to have $1.8 million:

• At a 3% yearly return, 30-year-olds would need to invest $2,447.42 a month for 35 years to reach $1.8 million.
• At a 6% yearly return, you'd need to invest $1,310.42 a month for 35 years to reach the same goal.
• At a 9% yearly return, you'd need to invest $668.24 a month for 35 years to reach $1.8 million.

How much 35-year-olds should invest each month to have $1.8 million:

• At a 3% yearly return, 35-year-olds would need to invest $3,110.35 a month for 30 years to reach $1.8 million.
• At a 6% yearly return, you'd need to invest $1,847.08 a month for 30 years to reach $1.8 million.
• At a 9% yearly return, you'd need to invest $1,057.51 a month for 30 years to reach the same goal.

How much 40-year-olds should invest each month to have $1.8 million:

• At a 3% yearly return, 40-year-olds would need to invest $4,058.67 a month for 25 years to reach their $1.8 million goal.
• At a 6% yearly return, you'd need to invest $2,661.58 a month for 25 years to reach $1.8 million.
• At a 9% yearly return, you'd need to invest $1,701.83 a month for 25 years to reach $1.8 million.

How much 45-year-olds should invest each month to have $1.8 million:

• At a 3% yearly return, 45-year-olds would need to invest a whopping $5,507.04 a month for 20 years to reach $1.8 million.
• At a 6% yearly return, you'd need to invest $3,969.67 a month for 20 years to reach $1.8 million.
• At a 9% yearly return, you'd need to invest $2,817.56 a month for 20 years to reach $1.8 million.

How much 50-year-olds should invest each month to have $1.8 million:

• At a 3% yearly return, 50-year-olds would need to invest $7,956.17 a month for 15 years to reach $1.8 million.
• At a 6% yearly return, you'd need to invest $6,273.70 a month for 15 years to reach $1.8 million.
• At a 9% yearly return, you'd need to invest $4,909.47 a month for 15 years to reach $1.8 million.

How much 55-year-olds should invest each month to have $1.8 million:

• At a 3% yearly return, 55-year-olds would need to invest a staggering $12,908.04 a month for 10 years to reach $1.8 million.
• At a 6% yearly return, you'd need to invest $11,078.73 a month for 10 years to reach $1.8 million.
• At a 9% yearly return, you'd need to invest $9,487.73 a month for 10 years to reach $1.8 million.

As you can see, the longer you wait to start investing, the more money you'll have to contribute each month to hit the same goal even if you earn a higher yearly return. That's why sooner is almost always better when it comes to putting money in the market, especially if you want to make $1.8 million.

Keep in mind that the stock market likely won't have the exact same return every single year; it may be higher in some years and lower in others. Also, as you age, you'll likely be advised to invest in less risky assets to better preserve your money against a market downturn, which means your returns may be lower.

At the end of the day, even if you're not able to reach a goal as lofty as having $1.8 million, it's better to invest something rather than nothing. Investing just $200 a month as a 30-year-old (assuming a 9% yearly return) will still get you $538,728.93 by age 65. Work with a financial planner you trust to get personal recommendations for reaching your financial goals.

At CNBC Select, our mission is to provide our readers with high-quality service journalism and comprehensive consumer advice so they can make informed decisions with their money. Every article is based on rigorous reporting by our team of expert writers and editors with extensive knowledge of investing products. While CNBC Select earns a commission from affiliate partners on many offers and links, we create all our content without input from our commercial team or any outside third parties, and we pride ourselves on our journalistic standards and ethics. See our methodology for more information on how we choose the best investing.

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