Money

Less than a third of Americans think they'll have enough money to retire—here's how to figure out how much you need

About two-thirds of American adults are concerned about not having enough money for retirement.

According to personal finance site NerdWallet, which surveyed 2,000 U.S. adults in June 2018, "only 32 percent of Americans say they're confident they'll have enough money saved for retirement by their desired retirement age based on their current rate of savings."

The concern makes sense when you look at the numbers: Americans have an average of $84,821 saved for retirement, and about a third of Americans have less than $5,000 socked away.

How do you know how much money is enough to last through your golden years? The answer is highly personal and depends on your lifestyle and spending habits, but there are a few basic guidelines to follow if you want to retire comfortably.

For starters, many experts, including co-founder of AE Wealth Management David Bach, say that if you set aside at least 10 percent of your income, you'll set yourself up to be fine. More is better: Bach adds that if you want to retire "rich," save 15 to 20 percent and, if you want to retire early, save 20 percent or more.

According to retirement-plan provider Fidelity Investments, a good rule of thumb is to have 10 times your final salary in savings if you want to retire by age 67. Fidelity also suggests a timeline to use in order to get to that magic number:

  • By age 30: Have the equivalent of your starting salary saved
  • By age 35: Have two times your salary saved
  • By age 40: Have three times your salary saved
  • By age 45: Have four times your salary saved
  • By age 50: Have six times your salary saved
  • By age 55: Have seven times your salary saved
  • By age 60: Have eight times your salary saved
  • By age 67: Have 10 times your salary saved

Determining how much you'll need all boils down to what you want your future lifestyle to look like and how much it will cost to fund it. Tony Robbins, best-selling author of "Money: Master the Game," factors that into his simple, two-step formula for finding your "magic number":

  1. Determine how much money it takes to maintain your lifestyle. "To clarify, this is not how much you earn, but how much you spend," Robbins notes on his blog. For example: "If you make $100,000 but live off of $80,000, then this number would be $80,000."
  2. Multiply that number by 20.

Once you have a number in mind, you can start working towards reaching that goal.

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.

No matter how you choose to save, the most important step is to open at least one account.

Next, follow these three steps so your money can grow over time:

  1. Contribute as much as you can. If you're funding a 401(k), the contribution limit for 2018 is $18,500 for workers under age 50. If you're funding a Roth IRA or traditional IRA, the maximum yearly contribution is $5,500 for workers under age 50.
  2. Automate your contributions. Have your employer do a payroll deduction or have your money taken out of your checking account and sent straight to your retirement account. After all, you can't spend money you never see.
  3. Get in the habit of upping your savings consistently. Do this every six months, at the end of each year or whenever you get a raise. Again, if you make this automatic by setting up "auto-increase," you won't forget to up your contributions, or talk yourself out of setting aside a larger chunk.

Don't miss: Here's how much money Americans have in their 401(k)s at every age

Like this story? Subscribe to CNBC Make It on YouTube!