How fast will this prepayment retire my mortgage?

Q: I have a mortgage of $150,000 @ 4.5% for 30 years for one year now. If I pay $1000 extra off principal every month, how soon will I have this mortgage paid off?

A: You should download HSH.com's Homebuyer's Calculator Suite to run the calculations you'll need for this (or any other) prepayment scenario you might wish. To answer your question: At the 13th month of your loan, if you start adding an additional $1,000 towards reducing the principal, you will end up with a 113 month total loan term, or just about 9.5 years.