Investing in stocks — or mutual funds that hold a variety of stocks — is the key to getting the returns you need to reach your goals. Fidelity Investments found that those with more than $1 million in their 401(k) accounts had more than 70 percent of their assets invested in equities.
How to Save $1 Million Starting at Age 25
Assuming a 10 percent return, you will need to save about $158 per month to have $1 million by age 65 if you start investing at 25. With a more conservative 6 percent annual return, you will need to stash $502 in savings each month.
The younger you are when you start saving, the less you will have to set aside each month to amass $1 million by retirement. For this reason, it's important to get into the habit of paying yourself first, starting with your first paycheck, said Kevin Smith, executive vice president of wealth management at Smith, Mayer & Liddle in York, Pa.
It's a good idea to have contributions to a workplace retirement account deducted from your paycheck automatically. According to Smith, you won't have a chance to spend the money, and you'll get used to living on what is left after you pay yourself first.
If there's not enough room in your budget to set aside 15 percent, save enough to get the full matching contribution from your employer, assuming your company offers a match for retirement contributions. Otherwise, you're leaving free money on the table.
Click through to learn the 10 most popular states to retire to this year:
How to Save $1 Million Starting at Age 35
If you wait until age 35 to start saving, you'll need to set aside nearly twice as much each month as if you'd started a decade earlier. Assuming a 10 percent annual return, you will need to save about $442 a month to have $1 million by age 65. With a 6 percent return, you will have to save $995 per month.
As you move up the career ladder and start earning more, you should increase your retirement contributions with each raise or bonus to make up for lost time.
"By slowly increasing your monthly contributions, even by a few dollars each month, this will then ease the stress of having less take-home pay," said Leslie Tayne, a debt attorney in Long Island, N.Y., and author of "Life & Debt."
It's important that individuals in this age bracket resist the urge to increase their spending as their income rises.
"One of the best tips to becoming a millionaire is to live within your means and stop living like a millionaire," Smith said. "Those more likely to be millionaires frequently are common, everyday Americans ranging from plumbers, construction workers and schoolteachers to laborers, salespeople and middle managers who developed sound financial habits early and put investment monies aside on a regular basis, while keeping expenditures in check."
How to Save $1 Million Starting at Age 45
You will have to save about $1,317 a month and earn 10 percent annually on your investments to have $1 million by age 65, if you wait until age 45 to start saving. With a 6 percent return, you will need to save $2,164 a month.
Setting aside that much each month can be especially challenging for parents who have kids in college. Nearly half of Americans place a greater importance on helping their children pay for school than saving for their retirement, according to a recent poll from RBC Wealth Management-U.S. Unfortunately, retired individuals don't have access to loans the way college students do.
Parents whose kids are currently away at school might want to consider downsizing to a smaller home in their 40s to lower their housing costs and have more money to set aside for retirement.
How to Save $1 Million Starting at Age 50
If you wait until age 50 to start saving, you will need to stash about $2,413 a month with 10 percent annual returns, or $3,439 a month with 6 percent annual returns, to have $1 million by age 65. Taking advantage of catch-up contributions can help you reach this goal.
In 2016, you can add an extra $6,000 to a 401(k), 403(b) or 457 plan for a maximum contribution of $24,000. Additionally, you can boost traditional and Roth IRA contributions by $1,000, bringing the total amount you can set aside in these accounts to $6,500.
People in their 50s shouldn't shy away from equities, either. Fidelity Freedom Funds, which are target date funds that automatically adjust asset allocation based on a retirement date, still include equity investments for those in their 50s. Being too conservative can hurt your chances of getting the return you need to reach $1 million by age 65.
It's clear that reaching your retirement saving goals is easier when you begin setting aside funds in your youth.
"Time is your friend," Kruzel said. "Start now and make saving a priority."
If you need help creating a plan to reach your saving goal, start by asking if your employer offers access to investment advice as part of your benefits package. Otherwise, consider meeting with a financial planner. You can find planners that charge by the hour, such as those in the Garrett Planning Network, or search online at GuideVine.com or NAPFA.org, the website for the National Association of Personal Financial Advisors.
RELATED: Check out the average retirement age in every U.S. state:
This article originally appeared on GOBankingRates.com: What It Takes to Save $1 Million for Retirement
More from GOBankingRates:
25 Secret Ways to Save Money at Target
17 Biggest Budgeting Mistakes You're Making
How to Get the Best Personal Loan Rates