As the chart shows, the amount you have to save depends a lot on how early you start. If you begin setting aside money at age 20, you have to save $239 per month to reach $750,000. If you start at age 30, though, that number nearly doubles: You need to save $460 per month.
"The difference between starting at age 20 and starting at age 50 is striking," Arielle O'Shea, NerdWallet's investing and retirement specialist, tells CNBC Make It. "Someone who consistently saves from age 20 is able to build a $750,000 balance by saving nearly 90 percent less per month than someone who gets a later start at age 50."
That's thanks to compound interest. Compounding makes a sum grow at a faster rate than simple interest, because in addition to earning returns on the money you invest, you also earn returns on those returns over time.
Ready to put your money to work? The simplest starting point is to invest in your employer's 401(k) plan, a tax-advantaged retirement savings account, or other retirement savings accounts, such as a Roth IRA or traditional IRA.
You can also research low-cost index funds, which Warren Buffett recommends, and online investment platforms known as robo-advisers.
Here's how much money Americans have in their 401(k)s at every age
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