One of the most daunting aspects of retirement is not knowing just how much it'll cost you and how many years you'll live once you stop working. Of course, you can do your best to guess at the first part of that equation, but good luck coming up with an answer for the second half.

Still, one thing you can do is take a long, hard look at your retirement savings, estimate your future living costs, and run those numbers against a variety of scenarios to see how long your nest egg is likely to last. In fact, we have a useful calculator that allows you to input your estimated Social Security benefits and anticipated income needs to see whether you'll have enough money as a retiree or whether you'll need to jack up your savings game.

Senior couple reviewing finances


Are you at risk of outliving your savings?

In a recent Transamerica survey, 43% of workers said that outliving their savings is their greatest fear -- more so than actually dying. Yikes! But given that most workers, including those in their 50s or older, are woefully unprepared for retirement, it's a valid concern. The Economic Policy Institute reports that over 40% of households aged 55 to 64 have no retirement savings to show for. Meanwhile, the median savings balance among older Americans is a less-than-impressive $17,000 -- hardly enough to last 20 years or more.

Of course, Social Security can, and should, factor into your ultimate savings equation. If you're eligible for benefits, there's nothing wrong with planning to use them as a means of supplementing your income. But if you think you'll get by on Social Security alone, think again. The typical beneficiary today gets roughly $1,360 a month, or $16,320 a year, in benefits. And that's hardly enough to maintain even the most frugal lifestyle possible. When you throw unavoidable expenses, like healthcare, into the mix, it's easy to see why independent savings are so incredibly crucial.

How will your savings hold up?

If you want to lower your chances of outliving your savings, you'll need to take a serious look at your nest egg and see how many years of income it's likely to provide. Thankfully, we've made that part easy with our easy-to-use calculator.

* Calculator is for estimation purposes only, and is not financial planning or advice. As with any tool, it is only as accurate as the assumptions it makes and the data it has, and should not be relied on as a substitute for a financial advisor or a tax professional.

To use this tool, simply do your best to estimate your monthly living costs. You probably won't get an exact figure, especially if you're still a decade or more away from retirement, so just do your best. From there, input your expected Social Security income, pension income (if applicable), and any additional monthly income you plan on collecting. Finally, input your current retirement savings balance, and do your best to anticipate the yearly return it's likely to deliver.

That last part may be a bit tricky, but generally speaking, if you're invested heavily in stocks, you can easily hope for an average annual 7% return. If you're evenly split between stocks and bonds, go with a 5% to 6% return to be on the safe side. If you're more bond-heavy, give yourself 4%. And if you expect that money to mostly sit in cash, knock that return all the way down to 1%.

From there, it's a simple matter of letting our calculator do its thing and seeing what sort of results you get. If you're not happy with that number, then you'll need to rethink your retirement plans or make some changes to ensure that you don't run out of savings. You might, for example, look at postponing retirement for a number of years to boost your nest egg or alter your investments to increase your return. You might also consider scaling back your lifestyle to reduce the amount of income you'll need each month.

There are a number of adjustments you can make to improve your savings-related outlook, so play around with different scenarios to see what works best for you. Just don't make the mistake of sitting back and letting destiny run its course -- because if you do, you risk joining the ranks of the countless Americans who do indeed realize the fear of running out of money in retirement.