BOSTON (TheStreet) -- So just how good is your 401(k)?

It's hard to know. Answering that question is the catalyst behind BrightScope.com, a company started in January by two brothers, Mike and Ryan Alfred, to uncover the good, the bad and the ugly of employee-retirement plans.

The company has developed a database for 401(k) information that allows visitors to its Web site to punch in a company name and see a rating for their plan, along with the data used to develop that report card. Included among the more than 2,000 statistics are net plan assets, the number of participants, fees, the average account balance, service providers and top investment holdings.

The information is culled from government agencies, plan prospectuses and plan sponsors. Increasingly, information is being willingly provided by the companies being rated.

Among those it ranks as having the best 401(k) plans are: Saudi Arabian Oil, Lockheed Martin, Southwest Airlines, Piper Jaffray, FedEx, Amgen, Chevron, Exxon Mobil, AstraZeneca, IBM, OppenheimerFunds and Microsoft.

A sampling of the lowest-rated company 401(k) offerings include Darden Restaurants, Big Lots, RadioShack, Zale Corp., Bob Evans Farms, Best Buy, Whole Foods Market, La-Z-Boy,Wal-Mart, Home Depot and Tyson Foods.

By comparing companies within peer groups, broad discrepancies are illustrated. A worker at Darden Restaurants, assessed a rating of 35, would have $449,000 in lost retirement savings, necessitating 23 years of additional work to close the gap compared with a top plan. At Bob Evans Farms, it would take 27 years, and at Wal-Mart, 22 years.

A telling indicator is the average account balance. The average of Saudi Arabian Oil's 2,900 participants is $470,000. The 40,000 employee participants at Whole Foods have an average of $4,300.

Many of the best plans are grouped within industries. Oil companies, for example, tend to offer more robust benefits. By contrast, many retailers -- in part because of the transient nature of their employers, the prevalence of part-timers and a lack of participation -- have worse plans.

Read More:   401k, your nest egg