Principal Financial Group Inc. has come up with a tool that can help retirement plan participants estimate when balances might return to Jan. 1, 2008, levels.

Principal, Des Moines, Iowa, says the tool asks each user for the user’s Dec. 31, 2008, account balance, total combined annual employee and employer contributions, and anticipated rate of return.

The tool shows users how increasing their own contribution rate can help them recover from the market downturn, Principal says.

The tool is available at http://www.principal.com/rebuild