For some fun, calculate it here at this wonderful website chock full of great financial tools and tips–Choosetosave.org:
Choose to Save® provides Internet tools . . . to help consumers plan all aspects of their financial security, and includes the award-winning Ballpark Estimate Retirement Planning Worksheet to estimate how much they need to save for retirement. Additional Choose to Save® materials include a series of booklets, such as The Power to Choose, as well as brochures such as The Top Ten Ways To Save for Retirement, from partners like the U.S. Department of Labor (call 800-998-7542). Many other informational brochures are also available. Choose to Save® was created by the nonprofit, nonpartisan Employee Benefit Research Institute (EBRI) and its American Savings Education Council (ASEC).
Also, you can take this very interesting Retirement Income Quiz here.