A blended payment contains an interest portion and a principal portion. The total of the two for each payment always add up to the same amount.

Prepaying future principal portions (pre paying principal rule, PPP) of a blended payment is an excellent way to save on interest and if it done according to the amortization schedule you are immediately aware of your interest savings over the life of the mortgage. This can be done by simple addition but you must have an amortization schedule to perform the task.

** **

This example screen below, demonstrates, the prepaying principal rule, that if the total of all the principal portions of payments #13 to #24, are paid along with the 12^{th }payment.

The total savings in interest is the total of the interest portions of payments #13 to #24. The Interest and Principal columns from #13 to #24 are highlighted with the mouse so that the totals are shown on the bottom (Selected)