This calculator helps you to understand how much money you can accumulate by making monthly contributions to your 401(k) account. Enter the amount you plan to add to your account each month, and the expected interest rate. The calculator will show you the amount that will accumulate in the account over different time spans.
It is particularly interesting to note the massive difference between the 30 and 40 year numbers. Getting started at age 25 rather than 35 can have a BIG impact!