A new Transamerica Center for Retirement Studies survey found that $1 million is the median savings balance people estimate they’ll need for retirement. But with forecasts calling for low investment returns in the years ahead, building a seven-figure nest egg is a challenge. Here’s how to pull it off.

Many people have been able to save impressive sums for retirement. Some 630,000 IRAs had balances greater than $1 million, according to a 2014 Government Accountability Office report. And Fidelity Investments said earlier this year that more than 72,000 of the 401(k) participants in its database had accounts valued at $1 million or more.

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But most of these people built those balances in an era of generous investment returns. Between 1926 and 2014, for example, large-company stocks gained an annualized 10.1%, while intermediate-term government bond returned 5.3% annually, according to the 2015 Ibbotson Classic Yearbook. During the go-go 90s annualized gains were even higher—18.2% for stocks and 7.2% for bonds. Today, forecasts like the one from ETF guru Rick Ferri call for much lower gains, say, 7% annualized for stocks and 4% or so for bonds.

Which makes accumulating a seven-figure nest egg a more daunting task. Consider: Save $1,000 a month and earn a 7.5% annual return—reasonable based on historical returns for a 70% stocks-30% bonds portfolio with annual expenses of 1%—and you’ll get you to $1 million in 27 years. Drop that return to 5% after expenses—what a 70-30 portfolio might earn based on current forecasts—and it takes 33 years to reach $1 million.

People can disagree over whether $1 million is a legitimate target. Clearly, many retirees will need less, others will require more. But whether you’ve set $1 million as a target or you just want to build the largest nest egg you can, here’s how to reach your goal given diminished expectations for returns.

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1. Get in the game as early as possible—and stay in as long as you can. The more years you save and invest for retirement, the better your chances of building a big nest egg. Here’s an example. If you’re 25, earn $40,000 a year, receive annual raises of 2% during your career and earn 5% a year after expenses on your savings—a not-too-ambitious return for a diversified portfolio of stocks and bonds—you can accumulate a $1 million account balance by age 65 by saving a bit more than 15% of salary each year. That’s pretty much in line with the recommendation in the Boston College Center For Retirement Research’s  “How Much Should People Save?” study.

Procrastinate even a bit, however, and it becomes much tougher to hit seven figures. Start at 30 instead of 25, and the annual savings burden jumps to nearly 20%, a much more challenging figure. Hold off until age 35, and you’ve got to sock away more a far more daunting 24% a year.

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Of course, for a variety of reasons many of us don’t get as early a start as we’d like. In that case, you may be able to mitigate the savings task somewhat by tacking on extra years of saving and investing at the other end by postponing retirement. For example, if our hypothetical 25-year-old puts off saving until age 40, he’d have to sock away more than 30% a year to retire at 65 with $1 million. That would require a heroic saving effort. But if he saved and invested another five years instead of retiring, he could hit the $1 million mark by socking away about 22% annually—still daunting, yes, but not nearly as much as 30%. What’s more, even if he fell short of $1 million, those extra years of work would significantly boost his Social Security benefit and he could safely draw more money from his nest egg since it wouldn’t have to last as long.

2. Leverage every saving advantage you can. The most obvious way to do this is to make the most of employer matching funds, assuming your 401(k) offers them, as most do. Although many plans are more generous, the most common matching formula is 50 cents per dollar contributed up to 6% of pay for a 3% maximum match. That would bring the required savings figure to get to $1 million by 65 down a manageable 16% or so for our fictive 25-year-old, even if he delayed saving a cent until age 30. Alas, a new Financial Engines report finds that the typical 401(k) participant misses out on $1,336 in matching funds each year.

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There are plenty of other ways to bulk up your nest egg. Even if you’re covered by a 401(k) or other retirement plan, chances are you’re also eligible to contribute to some type of IRA. (See Morningstar’s IRA calculator.) Ideally, you’ll shoot for the maximum ($5,500 this year; $6,500 if you’re 50 or older), but even smaller amounts can add up. For example, invest $3,000 a year between the ages of 25 and 50 and you’ll have just over $312,000 at 65 even if you never throw in another cent, assuming a 5% annual return.

If you’ve maxed out contributions to tax-advantaged accounts like 401(k)s and IRAs, you can boost after-tax returns in taxable accounts by focusing on tax-efficient investments, such as index funds, ETFs and tax-managed funds, that minimize the portion of your return that goes to the IRS. Clicking on the “Tax” tab in any fund’s Morningstar page will show you how much of its return a fund gives up to taxes; this Morningstar article offers three different tax-efficient portfolios for retirement savers.

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3. Pare investment costs to the bone. You can’t force the financial markets to deliver a higher rate of return, but you can keep more of whatever return the market delivers by sticking to low-cost investing options like broad-based index funds and ETFs. According to a recent Morningstar fee study, the average asset-weighted expense ratio for index funds and ETFs was roughly 0.20% compared with 0.80% for actively managed mutual funds. While there’s no assurance that every dollar you save in expenses equals an extra dollar of return, low-expense funds to tend to outperform their high-expense counterparts.

So, for example, if instead of paying 1% a year in investment expenses, the 25-year-old in the example above pays 0.25%—which is doable with a portfolio of index funds and ETFs—that could boost his annual return from 5% to 5.75%, in which case he’d need to save just 13% of pay instead of 15% to build a $1 million nest egg by age 65, if he starts saving at age 25—or just under 22% instead of 24%, if he procrastinates for 10 years. In short, parting investment expenses is the equivalent of saving a higher percentage of pay without actually having to reduce what you spend.

Who knows, maybe the prognosticators will be wrong and we’ll see much higher returns than they expect, making it easier to accumulate $1 million, or whatever sum you’ll need to provide adquate retirement income. But if you follow the three guidelines I’ve laid out, you’ll improve your retirement prospects either way.  (5/19/15)

Walter Updegrave is the editor of RealDealRetirement.com. If you have a question on retirement or investing that you would like Walter to answer online, send it to him at walter@realdealretirement.com.