Although it may appear complicated, grading sewing patterns is based on a few simple rules with definite numbers added to very specific parts of the pattern for each size up and down the size chart. These rules are used in repeat for all garments within a category (mens, women's or children). The image below is of a black fitted dress block graded from Size 8 to Size 10 by cutting through the crucial grade points and adding the extra required to go up one size in the pattern. The white lines are these crucial grade points where the extra is added. It is the example I use in my pattern making classes to assist in the understanding of where patterns grow between sizes.
