Thanks Zamboni.
Yeah, one thing that is a little unrealistic though is that the calculator assumes that all of the new investment for each year gets put in right at the beginning of the year. In reality, most of us are putting small amounts in bi-weekly into our 401K's, Roths, etc. So, my calculator gives a slightly overinflated number, since in reality capital for each new year is injected throughout the year.
I didn't want to take the time to figure that out, so as a workaround, I suggest just thinking "hmm, the real number will in actuality be close to, but a little smaller than this"!!