The 401(k) plans many U.S. workers will rely on when they retire are getting a good going-over at BrightScope, a new Web site that lets plan participants and sponsors see how their 401(k) measures up against the competition.

BrightScope rates 401(k) plans with a single number between 1 and 100. To arrive at that rating, it gathers more than 200 pieces of information on factors including a plan's administrative and investment costs, average salary deferral and the company match, and vesting schedule, and then runs thousands of simulations to arrive at an estimate of how long it would take the average participant to save enough for retirement, compared with the plans provided by a group of the company's peers.

BrightScope started by rating 1,000 companies based on publicly available data, such as the Form 5500 that employee benefit plans must file with the government. But CEO Mike Alfred says the company has now heard from "several hundred" companies, mostly large ones, eager to provide information about their plans in order to improve their rating. Once companies become aware of the Web site, Alfred says, "their first inclination is to make sure the data being used to score the plan is as current and as accurate as possible."