by Center for Personal Finance editors

WASHINGTON (4/21/08)--Even if you've been diligently directing funds into your company's 401(k), hidden charges may be slowly taking a bigger bite from your nest egg than you think (Kiplinger's May 2008).

A study released last year by AARP revealed that 83% of 401(k) plan participants don't know how much they're paying in fees, and 54% say they don't feel knowledgeable about how those fees affect the balance of their retirement savings.

Investment fees--which make up the brunt of the fees you pay--aren't easy to calculate. And don't expect to find a line item on your statement that spells out the costs. To figure out what you're paying for investment fees, use the investment fees calculator at Bankrate.com, or follow these steps:

• Go to your 401(k) Web site and look for the expense ratio--expressed as an annual percentage of your total investments--for each fund in your portfolio. Or, look it up using Kiplinger's Fund Finder at Kiplinger.com/tools/fundfinder.

• Write each expense ratio beside the balance in each fund listed on your statement. Multiply the expense ratio by your ending balance, which is the cost of each fund. If the ratio is 0.55% and your balance is $30,000, you're paying $165 a year in direct investment fees.

• Then, add up all the expenses for all the funds you own and divide that into your total balance. If your total expense ratio is 1% or less, that's considered reasonable.

Even a one-percentage-point difference adds up to big bucks over time. If you think your plan's expenses are too high, talk with your boss or a human resources representative to see if there are lower-cost alternatives.