If I asked you right now how much you're paying in 401(k) fees, would you know the answer? If not, you're not alone.

In fact, if you did know the answer, you'd be in the minority. A whopping 92.6% of Americans don't realize exactly how much they're paying in hidden fees related to their 401(k) plans, according to a NerdWallet study, and those fees can put a major crack in your retirement nest egg.

Over a lifetime, those hidden fees can amount to over $155,00 for a medium-income, two-earner household, according to calculations by think tank Demos, and higher earners stand to lose even more -- up to $278,000.

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No fees, please

There's a reason why most people are unaware of what they're paying in fees -- 401(k) providers don't make it easy for you to find out. When you receive your statement telling you how much you've earned, all you typically see are net returns with the fees already subtracted from your total. But just because you don't see any fees listed on your report doesn't mean they're not there.

There are over 28 different types of fees you could find buried deep within your plan, going far beyond the expense ratio that covers basic operating expenses. While this statistic (which covers management, marketing, and administrative fees) is the most visible, it's far from the only one. There are also possible trading fees, which can include shareholder fees and other plan-level fees that are specific to each 401(k) provider. 

Retirement plan providers can be tricky, so even if you do dig through the fine print to see how much you're paying in fees, it may not look like much. According to the Demos study, the average person pays about 1.27% in expense ratio fees and an additional 1.2% (on average) per year in trading fees.

Paying just 2.5% in fees may seem minimal, but, according to the study, it can cost investors about a third of their total earnings over a lifetime.

Say, for instance, you have $45,000 saved already and are planning on retiring in 25 years. Assuming a rate of return of about 7% compounded annually and that you're making no additional contributions, here's where you'll end up depending on how much you're paying in fees:

Fees Amount accumulated after 25 years
0%  $244,235
1.5% $171,603
2.5%               $135,245

So 2.5% may not seem like much, but it can shave over $100,000 off your total earnings after 25 years. 

How much are you paying?

The first step in saving money in fees is figuring out how much you're actually paying. Unfortunately, though, 401(k) providers don't make it easy to find this information.

You can start by checking out your plan's prospectus, which will cover all of the expenses involved in different investment options. However, this document is often difficult to maneuver and can sometimes be hundreds of pages long, filled with complicated financial jargon.

An easier option is to use a resource like Morningstar to analyze the fees in your plan. With Morningstar, simply input your investment, select the Expense tab, and your fees will pop up.

There are also other resources, such as the site It's Your Money, which will automatically calculate how much you're paying in fees based on your 401(k) plan. After plugging in the company you work for and the name of your provider, the site will tell you what you're paying and how it'll affect your investments over the long run.

It's also important to remember that a number alone won't do you much good. After you find out what you're paying, you'll need to compare it to other plans to see if you're getting a good deal. Every plan will have fees of some sort, so it's just a matter of finding one that will cost less than the others.

What if the fees are too high?

If you're paying an outrageous amount in fees, your first option is to see if there are other investment choices available at lower costs.

401(k) plans can be tricky since you're at the mercy of your employer in terms of your investment options, so you may not have many choices. In that case, your best bet is to talk to your plan administrator to discuss fees. Although advisors are typically hesitant to lower fees on their plans (since that's how they make their money), it is possible to negotiate for lower fees.

Before going in, though, you can arm yourself with knowledge by using BrightScope to see exactly where your company ranks compared to its peers. By plugging in your company name, the site will give it a score between 0 and 100 based on a variety of factors. If your company has a low score, you may have more bargaining power.

If your provider isn't budging on fees, you also have the option to take advantage of an IRA. IRAs give you more investment options, so you can choose the ones with the lowest fees. You'll have to shop around first and do your homework to make sure it makes financial sense to switch to an IRA, but it could make the difference between retiring early and comfortably and having to work another 10 years to make up for what you lost.

Katie Brockman has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.