You might have heard your factory, patternmaker, or grader refer to a 1” or 2” grade and wondered what exactly they meant.
A 1” or 2” grade refers to the total amount the body circumference changes between sizes. This refers to chest measurement for tops and dresses or waist measurement for pants and skirts. Other points of measure are graded in different increments, but in proportion to the garment size and the body circumference grade amount.
This grade amount does not always refer to all sizes, but only the difference between the base size and the sizes right above and below it. It is common for the body circumference grade to be smaller for the smallest sizes and get larger as the sizes go up.
A 2” grade is typical for alpha sizes (i.e. XS-XL) while a 1” grade is found in numeric sizes (i.e. 0-20). The smaller difference between sizes in a 1” grade means that there are more sizes, but your customers can find a size that fits her more precisely. Certain types of products and sizes can have a 3” or 4” grade.
The inch-grade names are simply a handy way to refer to the overall sizing and grading strategy for a garment.