Enter your normal mortgage information at the top of this calculator. Then add any other additional payments you would like to make be it one-time, weekly, monthly, quarterly or yearly. Then click on the calculate button to see your results.
If you would like to make multiple payments for ranges of time you can enter multiple one-time payments or other periodic payment types by clicking on the "Add Payment" link. The calculator is quite flexible. You could add 360 extra one-type payments or you could do an extra monthly payment of $50 for 2.5 years and then an extra monthly payment of $100 for 3 years, etc.
Once you have filled out all your information click on the calculate button to see the side-by-side results for your old loan and the loan with extra payments made.
At the bottom of the calculator there is also an option to turn on displaying a monthly amortization schedule with your results.