We have plenty of calculators that tell you how much you can save in interest charges buy making an addition to your regular payment. This calculator address the special case where you want to make a bi-weekly payment instead of monthly. The theory is that you will knock off a little extra interest payment by paying each month twice. Some online companies offer to do this for you. We do not recomment this arrangement. Why pay an outside company a fee when all you have to do is add extra to your regular payment? So this calculator will compare making a bi-monthly payment or paying a little extra on your monthly payment..