There are many different ways to attach a railing to a deck. For this calculator it is assumed that the post exterior matches the pale in width. If you have a 5 1/2" width of the pale the post would consist out of a 2 x 6 to support the pickets and the rails. This 2 x 6 is screwed into the rim joist with a bevel cut at the bottom lapping a 9" rim board by 8". Often the pales come in a pre-cut length and to keep the required railing height you can't do the same with the pales. However, if you are cutting the pales you could do the same with the pales. But whichever way you choose to do this, the amount of post is subtracted from the pale count in this calculator and since we are counting the exterior part of the post the corners area L shaped and will count for two.
Amount of Pales calculated with 4" of spacing