The No. 1 question when people are considering retirement is exactly how much money will they need.

It’s of course possible to get rough estimates for some of your living costs, but things like inflation, sudden health problems and medical bills, tax increases and Social Security running short of money are things totally out of your control.

So even if you’ve done a good job of saving through the years, you still might come up short if a sudden expense wipes out a chunk of your nest egg.

Fidelity says older workers should stash away 10 times their ending salary by age 67. But global professional services firm Aon says in a recent report that the average retiree will need about 16.4 times his or her ending salary to cover the full costs of retirement.

If that sounds like an unattainable goal, here’s the good news: About 5.3 of the 16.4 number will come from Social Security benefits.

The bad news: By age 67, the average worker will only have about 7.9 times their final salary in savings through a 401(k) or pension.

That leaves the average soon-to-be retiree about 3.2 times short of the 16.4 figure recommended. That might not seem like such a big deal, but when you look at actual dollar figures, things get a lot more concerning, especially for top earners.

If you earned $200,000 a year at the end of your career, you’re going to be short $640,000 missing that 3.2 figure.

But say you only make $50,000 that final year. Welp, you’re going to be short $160,000, which is no small chunk of change.

Let’s go even further with the $50,000 figure and assume you’ll live to be 85 years old. Averaged out, you’re going to be short nearly $9,000 a year.

Making up for lost ground

If you’re nearing retirement age and are far short of what you need, you’ll have to do everything possible to sock away as much of your salary as you can. But even just $100,000 short of what you need will take drastic measures in altering your lifestyle to make up what you’re missing. You can get a second job, but who wants to spend a few years working every waking moment of the day at two jobs?

Your next best bet is to downsize your home or move to a 55+ community, where homes generally are less expensive. You can cut what you pay for property taxes and possibly upkeep, utilities, etc. If you rent, do the same thing and downsize as much as you can, or even move to a part of the country with a lower cost of living — here’s what it costs in each state — to stretch your money further.

You also will have to temper expectations upon retiring. You might want to spend a lot of time traveling, but you might have to scale back and stick to day trips or fewer trips altogether.

You might also have to consider working at least part-time to supplement your income. Working 10-15 hours a week can also help occupy some of your new-found free time.

You might consider extending your career a couple of years to make up the shortfall. If you were going to retire at 65, maybe stick around until you’re 67 or 68 and delay taking your Social Security benefits, which also will raise your monthly payouts.

If 16.4 times your final salary seems like too much just remember, it’s one of many estimates you can find and not necessarily the end all, be all when it comes to figuring out what you’ll need. But in the meantime, it’s not a bad goal to shoot for. If you can stick with it and make it there, you’ll have all the money, time and freedom you’ll likely need in your golden years.