Retirement is becoming more expensive every year. With general living costs increasing, healthcare expenses skyrocketing, and financial safety nets like pensions and Social Security becoming less reliable, retirees will need to save more than ever.

Saving $1 million for retirement may sound impossible, but it's more realistic than you may think. Even if you're not wealthy and can't afford to invest thousands of dollars every month, it is possible to turn $100,000 into $1 million. Here's how.

Young person putting a folded bill into a piggy bank

Image source: Getty Images.

1. Invest in S&P 500 index funds

Picking stocks can be challenging, especially for those who may not enjoy spending hours every week researching different companies. Fortunately, there's an easier way to invest while still reaping the rewards.

An S&P 500 index fund is an investment that includes hundreds of stocks from leading U.S. companies. All of these stocks are bundled together into a single fund, so you never need to worry about choosing individual stocks.

S&P 500 index funds are fantastic "set it and forget it" types of investments, and they perform best when they're left alone for long periods of time. So to make the most of this investment, all you need to do is invest regularly and then sit back and watch your money grow.

2. Invest consistently

Consistency is crucial when investing. Even if you can't afford to save much, investing on a regular basis can help grow your savings more than you think.

Say, for example, you currently have $100,000 saved for retirement, and your investments are earning an average rate of return of around 10% per year. If you were to invest just $50 per month, you'd have more than $1.1 million accumulated after 25 years.

Preparing for retirement is also easier when you set saving goals each month. By investing a set amount every single month, you're more likely to stay on track than if you only invested sporadically.

3. Earn your full 401(k) match

Matching 401(k) contributions from your employer can potentially double your savings, so it's wise to take advantage of them.

The average 401(k) match is around 3.5% of a worker's wages, according to data from the Bureau of Labor Statistics. Say you're earning a salary of $50,000 per year. That 3.5% match would amount to around $1,750 per year in contributions from your employer.

That may not seem like much, but it can add up significantly. If you're earning a 10% average annual return on your investments, $1,750 per year would amount to roughly $775,000 after 40 years.

That's only the money from your employer. Once you factor in your own 401(k) contributions, you'd have at least double that amount in total.

4. Avoid making withdrawals

When money is tight and you're faced with an unexpected expense, it can be tempting to pull cash from your retirement fund. But even relatively small withdrawals can have an enormous impact on your long-term savings.

If you withdraw money from a 401(k) or traditional IRA before age 59 1/2, you'll typically pay a 10% penalty and income taxes on the amount you withdraw. Depending on how much money you take from your retirement account, that could end up costing you hundreds or even thousands of dollars in fees and taxes alone.

In addition, withdrawing from your retirement fund will hurt your long-term earnings potential. Compound interest helps your money build faster the more time it has to grow. By withdrawing money from your account, you're reducing your balance and limiting your money's growth potential.

Of course, in true emergencies, you may have no choice but to tap your retirement savings. But do your best to build a solid emergency fund so that you can avoid withdrawing from your retirement account.

It's possible to retire with at least $1 million even if you're not rich, but you'll need to be strategic about it. By making these four money moves, you can maximize your savings and retire more comfortably.