[gvibes]

For a looooooooooooooong retirement, I think a 4% withdrawl rate is good number (that's return over inflation).

How much do you want to live on? 50k a year (today's dollars) sounds like a nice round number for a modest retirement. You would need $1.25M (once again, in today's dollars) to retire on.

Let's assume a 6% real rate of return on your investments up until retirement. That's a little opitimistic, I think, but whatever. To hit the 1.25M number, you would need to deposit roughly $3500 a month (also in today's dollars - ie the amount you deposit monthly will need to increase to keep up with inflation), assuming you start with nothing. That's quite a bit of scratch.

EDIT: my math sucks, so I could be badly wrong here, but that sounds about right.